How to reproduce

1. Give a piglin a gold block and a raw gold block. The command 

/data get entity @e[type=piglin,limit=1,sort=nearest]nventory

 results in 

[{id:"minecraft:gold_block",Count:1b}],{id:"minecraft:raw_gold_block",Count:1b}]

1. Use the command 

/item replace entity @e[limit=1,sort=nearest,type=piglin] villager.0 with air 1

Expected Behavior: The gold block is removed.

Reality: the nbt is unchanged. Other commands such as data merge, data remove, and data modify also fails to remove the items from the inventory. 

Villager inventories are tricky to work with, and the only way to manipulate them as far as I know is to use /item replace. However, piglin inventories, dispite working exactly like villagers, cannot be modified using the command.