Yesterday when I was playing on the latest snapshot 21w39a, I tried to kill an Iron golem and when I hit it and it started to follow and target me, it started to move his head constantly and repeatedly toward me! I did the same thing to a creeper and it did the same; but in spite of these mobs, other mobs acted normally. Here's a video of this iron golem's behavior I've recorded: https://twitter.com/MoonMiner6/status/1444200053611114498?s=20
You can also watch the video at the attachments.