Hanging signs display the wrong variant in the sign UI

When typing on a hanging sign, the hanging sign UI only ever shows the horizontal wooden bar (side attachment) sign variant, and never the ones that hang directly from the block above.

Note that regular signs (both placed on walls and on the ground) show the different variants in the UI despite being the same ingame item used to place them. You would also expect hanging signs to display the different variants in the UI, but they do not.