I am not sure, if this is a bug, but in the deep dark, the player only should activate the sculk sensors, so they don't just come in and see a bunch of wardens. The problem is, the bats activate them, so the player can sneak to the deep dark and see a bat activating a sculk sensor and summoning the warden.
Based on the fix to MCPE-153725 all winged mobs produce a level 2 vibration signal of the "flap" type.