The bug
Relates to MC-147516. Most mobs don't seem to look at their targets when attacking them in close range. The only mob that is almost facing at their targets is the piglin.
Related issues
is duplicated by
relates to
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Confirmed in 20w21a
Still in 1.16 Pre-release 2.
They also lower their arms when they do this
The mobs also randomly stop attacking, and provoking melee mobs (except piglins) take a long time to go hostile, melee piglins on the other hand look at their target when attacking at close range, and also have no random pauses and go instantly hostile if provoked.
Affects 20w27a
Can confirm for 20w46a.
Can confirm in 20w51a.
Can confirm in 21w03a.
In 23w33a