I don't think I was as clear as I should have been in describing the benefits of centering a scope before mounting it. And this is just what works for me guys. I am not trying to say if you do things differently that you don't know what you are doing. Based off my experience this is the best way to get the most out of any scope.
In general, using a scope at its center gives the best optical performance and turret repeatability while keeping the internals in the least amount of stress. A scope that works in a low stress environment at least in theory has a much greater chance of being a more durable and repeatable scope compared to one that is cranked toward its max and expected to hold its zero and provide consistent click adjustment for life. I have personally found this theory to be true in real world usage as well. So these benefits give me the best chance to keep my specific scopes working to their greatest potential. So part of my concept with this is that I am playing the numbers and doing everything I can to ensure that I am setting up the scope as perfectly as possible so it can do its job as well as possible over the longest period of time before failure.
Similarly, the signature rings aid with this concept because they allow a stress free environment when mounting a scope in rings and bases. Many guys don't realize this but almost always it is your scope that has to give when you have action/base/ring issues that are out of spec causing improper alignment. So in an example with a misalignment issue, with traditional rings you end up bending or torquing the scope tube in order to try to get in clamped down and aimed in the proper direction. This causes issues with all of the internals working correctly so before you even get to the centering of turrets concept, you have already induced stress in optical performance, turret repeatability and durability. Then add a scope that is trying to work on the edges of its turret adjustment and you can begin to see these little things turning into big things over time. Also, signature rings make it much more difficult to crush a scope with too much ring torque which puts stress on the internals as well. It should be noted that rifles with properly aligned mounting screw holes and straight bases and well machined rings will eliminate most of this issue as well so I am not making any such claim that the signature rings are the only way to skin this cat. But there are a lot of rifles that don't have all of this stuff lined up and there are a lot of guys that can't afford to get it fixed or can't afford to buy the best bases and high end machined rings and a really cheap and really effective way of handling it is to just use the signature rings. They are fantastic!
For years manufacturers have claimed that they believe around 60-70% of scope failures are due to improper mounting of a scope. A lot of guys poo poo this idea thinking it is just an excuse but once you begin to see these things at work I don't doubt that they are at least on the right track most of the time. I have seen all kinds of issues with scopes in traditional rings that are completely eliminated with signature rings. Things like the power ring having heavy spots in certain areas when adjusting power, to parallax turret or AO not working or working sporadically, to turrets not being repeatable or running out of adjustment quicker than they are supposed to. I have done a ton of testing on turret repeatability and click values as elevation reaches its max with scopes that are mounted vs not mounted and you would be amazed at the difference in some of those tests! Yes, the better made scopes do better in this regard but even they show effects and in some cases the big brand names are much worse than some of the mid level models.
So in a bit more detail, the concept of centering your turrets, whether you go to the extra effort of optically centering them or just getting close with a click count, is to get your turrets centered so you have a basic understanding that you have equal movement in all directions if needed. This is the location everything will work at its optimum level with the least amount of stress on internal components. The lenses are lined up perfectly so you theoretically get the best picture, read as most clarity, brightness, and resolution, while eliminating the most amount of issues, ie, CA, vignetting/tunneling, turret and parallax issues, lessened eye relief, more critical eye box, etc.
So the benefit of the Burris rings are that you can set your scope up to near perfect and then adjust the ring inserts to get you zeroed in at whatever distance you want. For me that is usually 200 yards. So I can bore sight or use whatever method I want to get POI and POA to match up but for this initial step I am only adjusting the ring inserts to get this initial stage completed. I personally throw my rifles in a lockable rest, pull the bolt, and perfectly center the target through the barrel. I then begin rotating the ring inserts until I get my reticle as close as I can to center of the target. I tighten the rings, take a shot and measure the distance I was off of center. Most times I can loosen the rings, taking care to keep track of where the inserts where positioned, and fine tune the inserts to get me even closer. Then I tighten back up, verify with another shot and then I am done with my initial zeroing.
Of course there is going to be some minor usage of the turret adjustment to get perfectly centered at your zero point. I think this is where I confused some folks. But the amount of adjustment needed to do this is very small, often times only a couple MOA, so I am still very close to centered up which is ideal. There is obviously a range of movement around the center where you loose little performance optically or mechanically speaking and the signature rings and beginning with a properly centered scope allows you to stay in this area as much as possible. I personally try to stay out of the top and bottom 1/4's of the adjustment range for all of my shooting. I feel this gives me an amount of adjustment that is very dependable and repeatable. Depending on my use and the specific scope I have this may or may not always work but I usually can get very close with this system. Some scopes can go further towards the extremes of turret adjustment and some can't. One of the reasons you should test every scope or in my mind play it safe and use this system, or one similar, so you give yourself the best chance to keep things repeatable.
Now a LR guy may not want to set up his scope to be centered at 200 yards because he mostly shoots at say 600-1000 yards. So he may want the best optical and turret performance at those distances. Plus he may need more elevation adjustment to get out to the farthest distances he shoots. This is still easily done with this system. With a centered scope, or if needed with a scope adjusted lower so you have more up elevation, you can then use the inserts in the same way you would use a sloped/canted base and can at the same time still use the inserts to get you on target if there are alignment issues on the windage plane.
Not sure if I have better explained or muddied the waters further!