In the past I have seen merges happen, where I explicitly commented before that there were still issues which make the ebuild don't work and asked for improvements before we proceed. I thought that limiting the group of people who merge to official devs would increase the quality.
But I think questioning this is right for two reasons, first as seen in the past, limiting to gentoo dev doesn't do what I expect it to do and second it really separate the skills we expect a contributor to have from what we think a dev owns. And as our goal is the raise independent new devs from our contributor group, and forcing the policy I wrote is counter productive to that goal.