In the latest snapshot, MC-303554 was fixed to make the custom component piercing_weapon function correctly with the damage penalty from the attack cooldown, as the default value for minimum cooldown was 0 when giving custom piercing weapons using commands.
However, this has had a big side effect on vanilla non-custom spear behavior, as the cooldown percentage of jab attacks now affects charge attacks, which can be seen when following up a jab attack with a charge attack (the charge attack has reduced damage based on the cooldown percentage of the prior jab attack).
This significantly harms the usecases for the jab attack and I don’t believe it was a conscious change, as it was not mentioned in the changelog despite being a big nerf.
I am not sure this is a bug, however I can confirm that this does happen.