Disabled items work like ghost items and are deleted in certain cases

Using saved hot bars to export disabled items into a new word the items act like ghost items.

Steps to reproduce:

1. Create a world with the "Update 1.21" experiment enabled.
2. Grab a bunch of "Update 1.21"-specific items and put them in the hotbar (for example, /give @s mace 9).
3. Save the hotbar (C+1).
4. Create another world, this time with the "Update 1.21" experiment disabled.
5. Load the saved hotbar (X+1).
6. Switch to survival mode and break some blocks/Reload the world/Open a chest/Run /data get entity @s Inventory.

Observed result:
The items disappear and act like ghost items.

Expected result:
The items do not disappear.