The Bug:
Airborne mobs that perish within the presence of sculk catalysts will cause sculk to spread, but not initially form.
Steps to Reproduce:
Place down a sculk catalyst on top of any blocks that sculk can replace.
Summon a mob that's airborne.
/summon minecraft:creeper ~ ~1 ~ {NoAI:1b,Health:1f}Kill the mob and watch the blocks beneath it closely.
Take note as to whether or not mobs that perish within the presence of sculk catalysts whilst airborne cause sculk to initially form.
Observed Behavior:
Airborne mobs that perish within the presence of sculk catalysts only cause sculk to spread and not initially form.
Expected Behavior:
Airborne mobs that perish within the presence of sculk catalysts would cause sculk to spread and initially form.
Linked issues
relates to 4
MC-249170
Sculk growth converts dirt with plant on top when on slopes
Open
MC-249285
Sculk catalysts don't spread sculk after killing the ender dragon
Open
MC-249262
Sculk cannot replace soul sand or mud when mobs die on top of them
Resolved
MC-262479
Sculk catalysts produce particles and noise when a mob is blown up at the same time the catalyst is destroyed
Resolved
This is intended behaviour. It is important to recognize that placement of a sculk vein is required for the sculk vein to spread thus sculk blocks to spread. Second important point in sculk design is that charges can only jump to sculk vein or sculk blocks. If you kill a mob on a platform of dirt with buttons on top, it will not spread the vein thus charge will not persist. If you kill a mob on a platform on sculk blocks with buttons on top, vein will not place, but sculk charge would be able to move to it via adjacency rules (so not obstructed with solid block faces), it will be able to move and continue roaming through sculk.