Correct. I can confirm it works, I was discussing with Harmattan mates about this and found this post. The wired1 connection that creates on PC (ethernet) it works on Android but not on N900 or N9 so by creating a mobile broadband access point you can use tthose phones modems over usb, Actually I tested a MVNO sim this way on my N900 and Debian. You have to know which are your operator's parameters to create the access point while on wired you don't know have to which apn you are using, the connection manager detects it.
BR
SteP