Found in 24w40a.

Create a non-experimental world and place a disabled block via a feature:

/place feature minecraft:pale_oak

Then, there are some weird behaviors: 

1. You cannot interact with it properly unless you press Shift.
2. The block placed via Shift + Right Click disappears immediately after placement.
3. Pick on it will get a ghost item.
4. The Piston will make these blocks disappear.

Other behaviors:

1. Can be saved and loaded.
2. F3+I can find the block entities.

Unlike entities such as The Creaking that disappear, these disabled blocks and items remain.