Roof cuts wall at bottom = no room definition?

[tundra_dweller]

While working on an addition plan using X16 beta I have a situation where I need a wall to have the "roof cuts wall at bottom" properties, and this particular wall lines up with an existing loft railing that defines the separation between the loft and open to below spaces. When I change this wall to have the roof cuts-WAB properties I lose my loft room definition. The fix for this is I can drag the loft railing across and under the RCWAB wall to get my room def back, which is how it would work in real life.

 

I don't recall RCWAB walls behaving this way before. I definitely don't recall being able to have two walls occupy the same space on the same floor level before unless using a pony wall. The RCWAB wall doesn't take on the "No Room Definition" property in the wall DBX. It seems like you might want to be able to select whether the wall defines a room or not maybe in a dormer situation or something.

 

So anyway I guess I'm wondering if this is something new with X16, or if I've somehow never run into this scenario before and its just the way roof cuts wall at bottom has always worked?