I was trying to create an enderman farm in creative to see if my design would work. I used the /summon command to get the endermite and the endermen did not aggrovate towards it. I have tested if they aggrovate with a spawn egg and they still don't. fyi I used /summon to give him special attributes.
Update: I tried just using ender pearls and the endermen started flowing in. Although I'm okay now, this still should be looked at.
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Thank you for your report!
We're actually already tracking this issue in MC-53518, so I've resolved and linked this ticket as a duplicate.
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I think this is an intended feature cause for whatever reason you want to spawn endermites in the end and dont want endermen aggroing.