Plating takes a full square just like a board now (due to being a big ol’ sheet of solid metal).
You shouldn’t have been able to put plating with a kitchen unit before anyway, I think it had the NO_REINFORCE flag on it… but that may have only stopped you putting plating on a kitchen unit, not the other way around.
The vehicle construction rules have been changed: Every square must now start with a frame, and other things go on top of that. This lets you put boards over wheels, for instance, and other part combinations that were not allowed before.