Expected Behaviour
Holding an item and left-clicking on a Bundle:
puts the held item in that slot and the player now holds the Bundle.
Holding a Bundle and left-clicking another item:
puts the Bundle in that slot and the player now holds the item that was clicked.
1.21.2 Pre-Release 1 Behaviour
Holding an item and left-clicking on a Bundle:
puts the held item in the Bundle and the player now holds nothing.
Holding a Bundle and left-clicking another item:
puts the clicked item in the Bundle and the player still holds the Bundle.
Summary
The expected behaviour (items are switched) is what happens with all other items in the game, including Shulker Boxes. The behaviour observed in 1.21.2 Pre-1 is what should happen when right-clicking. This would match what is already the button to remove an item from a held Bundle. Left-click to move item stacks; Right-click to interact with an item stack.
Comments 4
Interesting, but rather than speculate on how the error came about what was intended at what point, I'll instead illustrate how clear the error/inconsistency is.
Action | Bundle | Any other item |
|---|---|---|
Pick up entire item stack with empty hand | Left click | Left click |
Place down entire item stack in empty slot | Left click | Left click |
Place down item stack in occupied slot and pick up that item stack | Right click | Left click |
The 24w33a changelog states that:
The controls have changed from the original prototype:
Use left-click to put an item into a Bundle
So the “Holding an item and left-clicking on a Bundle” part is intentional, and
the “Holding a Bundle and left-clicking another item” part probably is intentional as well, as it is consistent with the behavior above. Which could makes this a change request.
Still, we need to wait for Mojang's confirmation though.