While playing on a multiplayer server I play on which runs 1.13 pre 4, I noticed 2 things. Creepers don't run away from cats in my creeper farm. There are literally 20 of them bunched up together and not moving or caring about the cat.
The other thing is enderman. In the enderman farm on this server we use the typical endermite aggression to get the endermen to move. In a big 50x50 square platform only 5-10 get aggrowed by the endermite, the other 30 just stay where they are, not getting aggrow.
They seem to just not react to other mobs like they normally used to. Regular mobs like zombies and skeletons still react to all other encounters
EDIT: Creepers also dont react to players when in sight or hit. (screenshot)
Endermen do get aggrow when you hit them
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