[STEP TO REPRODUCE]
punch mobs with attackKnockback items as a player.
[EXPECTED BEHAVIOR]
Depending on the value like most other attributes, mobs are knocked back.
[ACTUAL BEHAVIOR]
Regardless of the value, Mobs are knocked back only a certain amount.
Comments

This has been "fixed" in 24w18a.
The new
generic.attackKnockback
attribute only applies to illager beast entities.