SubViewport Cull Mask not working as expected

[meager atlas]

I am not sure why my SubViewport setup is not working.

I have a player with two sprites: The first is a Godot Icon (Layer Visibility 1) and the second a Red Square (Layer Visibility 10)

Then, I have a SubViewport with the world_2d set to the same as the players. This works as expected, rendering the world twice. (Picture 1)

If I remove Layer 10 from the SubViewport cull mask it correctly renders only the Godot Icon (Layer Visibility 1) and not the Red Square (Layer Visibility 10) (Picture 2)

However, if I instead remove Layer 1 it renders nothing. (Picture 3)

I'd expect it to render only the Red Square. I'm not sure what I'm doing wrong. Does anybody know by chance?
Happening on both 4.2.1 and 4.2.2

[meager atlas]

Here's the full project. You can press F1 and F2 to toggle layers in the SubViewports cull layer masks.
Toggling F1 works as expected (red square is hidden correctly) but toggling F2 seems to hide everything instead of just Layer 1