Indeed, while discussing AMP4Email, it seemed that, despite being a proposal in the AMP Project, all decisions for it's implementation were already made (and committed to) by the Gmail team, it had already been "reviewed" by a security team (although any such security protections are limited to Gmail's own internal protections, other implementers are on their own), and there seemed to be no opportunity for the greater email community to comment before these things were decided.

Having it up on GitHub after that doesn't really mean much. This is the same for Android and Chrome, of course.