It shouldn't hurt. Excessive clearance COULD affect accuracy but just skinning it should help if your equipment is consistent and you end up with uniform thickness.
All that's needed to know neck clearance is a simple measure of necks after firing. As mentioned, the chamber neck is ~1thou over this measure, as the brass sprung back from it. This is with normal brass that is not over annealed.
And even with little clearance(like 2thou), you do not have to neck turn for this. Clearance is clearance.
I don't know if you want to turn for low runout, or for lower neck tension, or both. Which is it?
As others have said Lapua brass is pretty consistent already. I doubt you will see any difference in performance by skim turning the necks of this brand of brass and your factory rifle. If you take off too much with that SAMMI chamber the brass will be overworked and it will cause neck splitting. (I know it did it) If you don't have the equipment to turn the necks AND dies to properly size the necks afterwards, you will spend money and time and might not see any improvement.
If you do try turning some necks please do a control with some unturned brass and for a comparison. When you are done testing please share this information with us.