Rank is supposed to be recalculated after annullment.
That in fact is the whole purpose of it.
I think there’s a bug right now, after the big rank update, where that’s not working at the moment.
I didn’t hear if that’s fixed or not.
(Edit: for the purpose of this discussion, I think we should assume that they do
(Another edit: RubyMineshaft said it’s been fixed 2021 Rating and rank adjustments - #610 by RubyMineshaft )