/drop with weapon slot can place items in the head slot

How to reproduce

1. Run the following command

   /drop entity @s weapon loot minecraft:chests/buried_treasure

   → Notice that it put items in your mainhand, offhand and head slot. It doesn't put items in any other part of your inventory

Note: The same happens when using weapon.mainhand. When using weapon.offhand, only the offhand and the head slot are filled with items