Mainly it explains both program and structure at the same time. Fixed programs are all poched, and among those fixed programs there are rooms that work as structure system- these are shown by thicker walls.
The reason we had all doors to room look like small pathways is that it's better to show how program can spill out: Fixed programs don't actually have completely closed part, but still can be pretty secluded area by having small pathways.
The plans are going to be rounded up (or be smoother) as it is being settled.
