Ah, right. I kind of missed this change, the original USB spec for the touchbook was (in fact, on the web page front still is ):

6 USB 2.0 (3 internal, 2 external, 1 mini)

Obviously there has been some port juggling going on there - I think the touchbook already has some sort of built-in hub/extra USB chip (IIRC the OMAP3530 has 3 host ports + 1 OTG).