While I don’t know if the warm neck will come onglued, it would probably be an easy fix if it does sometime in the future, it isn’t a critical system.Meanwhile I called Seaskin and they explained why the drain and extra room "issues" are "working as intended" (first drysuit that I bought so still I was not aware of some basic stuff).
The "potential ungluing" is a section of the warm neck that seems to be less glued than the rest (picture attached). Probably I'm nitpicking...