Are hidden achievements visible on xbox?

Question regarding both Xbox One and Xbox Series X. THough I assume it works the same on both consoles. How exactly hidden achievements work on xbox? Lets say I have a game that shows 30 (for example 0/30) achievements in xbox interface, I go through the list and see descriptions of every single achievement. Does that mean that the game can still have some hidden / secret achievements (like, they don't count to overal "30" number of achievements, and only show up on the list once unlocked.) Basically what I am asking, are hidden achievements shown in the xbox UI and count towards overall score while still hidden (just without names/descriptions)?