Nether generation based dimensions can have holes in the bedrock roof.

[Jaoheah]

In the dimension called "Peruz" (not sure if this is unique per player) It is basically the overworld but with nether generation and has lots of flowers. Some dirt spawns underneath the "Peruz" roof which occasionally has flowers that spawn on top of said dirt. breaking the bedrock. https://i.imgur.com/eLURdX6.png https://i.imgur.com/dxxMbkl.png