The cave floors or ceilings sometimes generate a huge flat surface area which seems unnatural, even the plains are less flat than this. The transition from floor or ceilings to the wall are jarring. We can see the floor generation is contrary to the ceiling or vice versa (sometimes both). They seems to generate quite more often with aquifers. There are no stronghold structure nearby.
I'm afraid this report would be mistaken as an opinion but I don't think this is intentional. Overall, I'm loving this new update and keep up the great work!
Edit: It seems the flat floors starts to appear on 21w10a but flat ceilings can be found since 21w06a