I'm not really 100% on the technical details, I'm assuming both a dropped weapon and a dead body are weaponHolders.
Observed:
When a unit dies, they drop their weapon and the body becomes a ragdoll. Assuming the weapon and body land close enough to each other, when the player opens the inventory on the body, they can pick up the weapon, even though it is in a separate weaponHolder.
However, when the player opens the inventory on weapon in the same situation, only the weapon is available (not the body).
Expected:
All items in close enough weaponHolders should be available, irrespective of which weaponHolder the player opens the inventory on.