Are you restricted by walls and ceiling when placing a new room to be ready?
I was wondering the same thing, but instead of hearing it from other fans, I wanted to hear it from the horse's mouth. I geekmailed the designers, Virginio Gigli and Simone Luciani and here are their responses:
Walls are only to help to see the groups. No effect on the adjacence rule.
walls and ceilings delimit the groups. They don't limit the preparation of new rooms.
Have a nice day.