Element Curve doesn't return Floor Boundary

I would expect the floor to cast to a curve as well, currently they are available as element dependents.

If you modify the floor it get more complicated and returns the boundary, not the creases. See this post RiR slab shape creases - #4 by Japhy

The rooms are more complex as well and have to go through the Analyse Spatial Element component Ehsan posted on the Guide.

No single solution for casting to curves on these elements unfortunately.