Knockback does nothing to sulfur cubes if they have a block inside

If a sulfur cube contains any block, attacking it with a weapon with the knockback enchantment will have no different effect to attacking it with something without that enchantment.

To reproduce:

/give @s wooden_sword[enchantments={knockback:5}]

Attack a sulfur cube with a block inside

Attack a sulfur cube without a block inside, or anything else

Note the difference in distance travelled

Expected results would be for knockback to have a clear effect, as is the case with all other entities.