Entities' limbs do not move upon being attacked when riding entities

The Bug:

When an entity is attacked, its limbs normally move, however, this isn't the case when they're riding entities.

Steps to Reproduce:

• Summon an entity riding another entity, for example, a piglin riding a horse.

• /summon minecraft:horse ~ ~ ~ {Passengers:[{id:"minecraft:piglin",IsImmuneToZombification:1b}]}

• Attack the piglin and watch its limbs closely as you do this.
• Take note as to whether or not entities' limbs move upon being attacked when riding entities.

Observed Behavior:

Entities' limbs do not move.

Expected Behavior:

Entities' limbs would move.