This question crossed my mind as well. But after a little thought, I've got an idea why?!

The fletchings on an arrow help it return to normal flight after getting off to a bad start. Finger shooters have much more of a problem getting their arrow to fly straight than a release shooter due to plucking or inconsistent release. With a release, this is much less of a problem.

However, that said, if I had any bare shafts, I'd be paper tuning with them and I'm a release shooter. I just can't imagine that over tuning is a problem unless you take it to an extreme. I guess I figure that I'd rather be sure all is well than find that my fletchings were masking a problem.