The bug

Note how in the attached picture, the zombie, which is dying, has dropped its iron sword, however it still appears to be holding said sword.

Similar arguments could be given for blocks held by endermen, heads of mobs killed by charged creepers, sheep wool, skeletons' bones, and so on. However, these should likely have their own tickets.

An easy way to fix this is to make mobs only drop items after the corpse disappears, like experience used to, eliminating this discrepancy.

How to reproduce

1. Run:

   /summon minecraft:zombie ~ ~ ~ {HandDropChances:[100f],HandItems:[{id:diamond_sword,Count:1b}],Health:1}
   

2. Hit the zombie.
   → Zombie dies and drops the sword as expected...
   →  but the zombie still holds the sword while it's already dropped