I wonder if some stuff was pulled because it was jet black and not the dark gray color. The assistant was like that when I was able to use it for those couple of weeks or so. It looked fine to me though, no complaints. however a lot of their dark mode stuff is really a dark gray. Just speculating,
also, from what I've been reading about the dark Gmail app and maybe Eric can verify this, is there is a switch in the Gmail settings to trigger it so that you can have it white or dark and not affect the rest of your overall dark mode. In effect, this would let you keep Gmail white if that was your preference