It's not exactly a bug. Just want to make a little stronger than this monster, or rather that the meeting with him was dangerous. It's not for you, but maybe you'll notice.
Mostly related to teleportation.
1. Teleported slowly, I wish he'd confused the player. That the player could not understand where he is.
2. It teleports from the player at a distance of about 10-15 blocks, so when he runs the player can already prepare for the impact. And if he suddenly appeared in front of the player it would be more difficult, as the player would not expect an appearance and was not ready.
3. (not necessarily, but as a fact if Enderman is in three blocks, he has to get a player when he stands on two blocks, because of his height he can do it).