IT IS!
Can the shaft be used as a timing mechanism during the swing ?
YUP.
Does the release point and release type influence the shaft flex or timing at all?
There is one perfect frequency shaft for every golfer—within every shaft type. Their is probably a better shaft type for each golfer as well.
But as far as frequency....there seems to be A NUMBER for every golfer, and that number rarely changes in the course of any swing upgrades or adjustments.
But!!!
Release points and types and triggers and aiming point and better, more powerful pivots, will ABSOLUTELY change your ABILITY to bend the shaft.
So, outside of perfect—on "your numba" fitting, a swing change will probably change you timing...and your shaft!