When blocks are placed under y=0, the current 16x16x16 area (a chunk) becomes loaded (see FIG 1). Afterwards when the block is removed (FIG 2) and the game is saved, the chunk reverts to its original state, with blocks inside the chunk. (FIG 3 & 4). The bug seems to only be active on pre 1.18 bedrock worlds (all worlds I tested are flat world settings) and the bug is active when all blocks of that chunk are broken.

edit: save and quit after placing down the block