Really, most ofthis is mostly irrelevant TBH.
This is a common point of confusion. Because of this, I think it is worth addressing and therefore relevant.
The official way of using the PKGBUILDs is manually with makepkg.
I suspect that the usual use case for interacting with the AUR is with an AUR helper. I think this qualifies it as subject matter that a capable package maintainer should have some familiarity with, even though this use case may be disagreeable to you personally.
the only times an AUR VCS package is out-of-date is when it's broken in some way
Assuming that AUR helpers are a common tool for interacting with the AUR, VCS packages in the AUR are out-of-date when their version number is... out-of-date. Finally, the situations that trigger a VCS package update should be identical whether a package is in the AUR or one of the more official repos. — Jeremy "Ichimonji10" Audet