Skip that touchy-feely-turney approach.
"IMHO, setting the sizing die so that it contacts the shell holder may or may not
be the correct thing to do for any given rifle."
Your honest opinion is 100% perfect. "May or may not" is not only the best answer, it is the RIGHT answer. My first reloading die purchase and 4-5 reloads later could have cost me some ill will. I followed exactly per manufacturer instructions which is wrong and had close call with incipient head separation. The Sinclair page is very good but being an engineer, I hate it when someone says "go by feel"! For many people that approach is so relative and most cannot feel .001 - .002. and even if they do, every single rifle is totally unique so one has to not only be able to feel but also feel for each rifle's characteristics. I am not saying some reloaders don't have some success doing this by feel or by manufacturer's instructions, but I have my paycheck betting the large vast amount of reloaders doing it that way and think they are just fine aren't in that .001 - .002 headspace range and those are the numbers to really shoot for (period).
There are a good number of tools that one can appreciate in your concern. Here are mine.
IMHO this tool cannot be beat but it does cost a few more dollars than some tools but it is so so worth it. Larry Willis's Digital Headspace Gauge.
Innovative Technologies - Reloading Equipment
I researched over and over and this tool just works, and works too good to now be without it.
Once you understand how to use the tool, (3 -4 shells possibly) you will question how anyone in this world can go by the "feel approach
" or the "turn 1/4 approach
". Not trying to be disrespectful to all but you will see that turning the die down even 1/16 - 1/24 of a turn (depending on die) makes the difference between .001 and .005.
This tool also works just TOO PERFECTLY for bullet seating depth in conjunction with Hornady's L&L OAL gauge and comparator. There are some considerations using this tool and Hornady's custom modified case in your OAL measurement but using this tool and Digital Headspace Gauge I think is super easy, fast and very accurate. (Having seen the homemade modified case approach fail because some bullets move when removing this case - Hornady's product or similar products are much better and much more accurate)
P.S. - A member on here - WOODS (he is in my opinion an experienced expert) - has different tool(s) to perform OAL and bullet seating and is very good too.
Call Larry Willis and talk to him. It will be 10 minutes of your time extremely well spent. (and no I do not work or personally know Larry except for this product sale)
Please guys - some of your instructions are setting people up for incipient head separation issues.
Again - Skip that touchy-feely-turney approach.