Drawing over an edge should face the whole L
It did not.
Drawing some diagonasl makes faces.
Removing those diagonals leaves the L shaped face intact.
This suggested that the vertices were not quite coplanar, but sufficiently coplanar to support one face.
However, looking again I see that the L shaped wall has a tiny gap in one corner so it won’t intersect and form a face !
Healing that gap allows the rectangle to intersect the wall !!! Or of course to form a face by over-drawing an edge.
