the bottom line. the water SHOULD never reach that point (plywood
sheathing) regardless, sticking it down or not sticking it down. but
that's not how it always goes, even in a perfect world.

Let me ask you this... if sticking it down doesn't matter, why isn't the
stuff sold without the adhesive as an alternative? Some marketing ploy?
Lawyers?

I'm still sticking it down on my new house...