So... I'm having an Enderman farm. When done looking at about 100 Enderman they keep teleporting all the time, as they teleport away if you look at them while they are close to you.
However... When I'm standing in the line from departure and destination they push me a little bit. Randomly.
As there are about 100 Enderman mad at me, teleporting all directions. Sometimes I'm even being pushed in the crowd, which results in near death situations.
So in summary: the Enderman is still a sort of Entity during the teleport. The whole thing of teleportation is instantly go to a place. Instead the Enderman is being moved to the destination very quickly (so not instant). When I stand in that line I'm being pushed.
I can't seem to be able to reproduce this (I am using glitched creative mode endermen). They can't move me when they teleport.