Hi Sean,
Attached the file. Thin stroke is not as bad.
It may be connected to my other post regarding starting point of stroke not rendered correctly when pressure is enabled, because when expanded the start of stroke will become a firework of nodes/vertices. And if no controller is enabled, so uniform brush width, this nodes Bonanza doesn't seem to happen.
Bonus Bug:
When stroke partially overlaps itself (for example at a sharp corner) sometimes it creates voids, which will be expanded as well. Image attached with red circle on the artifact (I also notice this in Illustrator CS6 so maybe it's a common vector problem).
Thank you.
Untitled_2.afdesign