Steps to reprocue

1. In the create world menu, select easy or peaceful difficulty.
2. Press the button to create the world.
3. Punch a tree log or dirt block and pick up the item.
4. Jump in lava or off of a tall cliff.
5. Respawn.

Expected result

You keep your item.

Observed result

Your item drops when you die. You do not have it when you respawn.

The changelog for 1.21.50 states that the new keep inventory in easy/peaceful addition would be added in 1.21.50. However, it has not been added.