You can perform inventory actions for a brief moment after death. This is a lot easily seen with moving a totem (which is supposed to prevent death) around the inventory. Easier to see the video attached for explanation.

How to recreate:

1) /gamerule keepInventory true

2) Hold a totem on your 1st slot and hold nothing in the 2nd slot and stay on the 2nd slot

3) Jump off a 30 block ledge

4) Hold the totem a split second before you hit the floor

5) You will die with a totem held on the death screen

It may require a few tries before this works.

Expected:

• Surviving the fall with the totem used or Dying without switching to the totem