Furred walls allow another exterior wall to hang over them. But, regular (frame-through) walls do not.
That is the lesson.
But, unfortunately, even if the furred wall seem to solve the issue, it caused another problem. Rooms cannot be formed if there is any furred wall in the layer.
CA doesn't seem to have the means to control the level of the exterior walls. They are overlapping with the beam; and hence, they conflict with the lower wall.
I don't know how people are designing the above types of structures (where you have two walls where one of them stands straight on top of the other). For now, I find no ways to put them together with proper walls defined. So, I deleted the foundation wall.