Warped Fungus and Crimson Fungus grown under any block will cause that block to break and disappear forever the picture below is an example.

Notes from MCPE-65757
At y=121, you can place warped/crimson fungi on their 'dirt' blocks, using bone-meal, they will sometimes clear out some bedrock blocks above them. Another way to fool it is putting warped/crimson blocks between the fungi and the bedrock and it let's it grow still.