Apparently, in the mobile update the Truffle Worm will spawn on ANY dry Mushroom Grass, even at the surface.
The Wiki may not reflect all of the update changes; it's maintained by the community and is not always accurate.
There are other threads where people are discussing the mobile update, it helps to search around.
a bridge (100 block minimum) of mud and spray it with blue solution. Then do something else, come back, and a few mushroom trees should be there to complete the biome and the music will start playing. Stand in the middle of that bridge wearing full turtle armor, water candle, and battle potion. Max spawn rate possible. BAM truffle worm
The Wiki may not reflect all of the update changes; it's maintained by the community and is not always accurate.
There are other threads where people are discussing the mobile update, it helps to search around.