GlytchMeister and everyone, sorry for the slow update: they got back to me.
They answer is in short: yes. it's the normal app behavior and there is no way to turn off this anywhere inside any of the proton android apps. Also, this won't change in the foreseeable future.
Personally, I find this very sad. I really like proton, but this is a break up reason for me. It will be a proper hassle, but I'm going for a new mail host. GOS is such a therapeutic experience without Google, and I strictly want to keep it like that. My takeaway: be the possibly less dependent on any mail provider, and just use domains for most of the things. I wish I would do that earlier, now it would save me loads of time. Anyway, lesson learned.
@TRInvictus Thank you for your comments on RethinkDNS! I'll also definitely deep dive into all of this as well.