If you have more resources open than the panes in the "pre-set" 3 vertical layout it won't give you what you ask for. Other presets seem to work.
Screenshot #1 - Layout when I just open a bunch of resources - 7 in total
Screenshot #2 - the 3 panel vertical layout I request
Screenshot #3 - the 7 panels I get



Seems like a bug to me. Anyone figure a way to get what you ask for?
Chris