When I gave a crossbow pigling a block of "gilded_blackstone", "nether_gold_ore" or "gold_block" they pick it up and with their empty hand they watch it as they normally do but when they finish watching, they keep their crossbow in their inventory and they put that block in the hand where his crossbow was. I was experimenting and just noticed what happens in piglings who use a crossbow, because those who use a sword keep the block in their inventory and keep the sword in their hand.