Crazy! At least it's a bug that can be worked around easily enough though.
Agreed it's unlikely anyone would set up such a 'moment' from scratch, but I discovered it when I went to edit an existing one.
If you choose "Add actions", it just shows every single room (though it mysteriously refers to them as 'devices'). I assumed it was overwriting existing actions (since those rooms were in the list as 'add-able'). It turns out it wasn't...
--------------------- 3 Channel Hubᴿ, 13xiTRVs, 8xRoomstats and 2xSmartplug/Repeaters. (UK)