I just got off the phone with the arranger expert at Roland US tech support and found out that what you read was in fact stated in error. There is no way to connect the GW7 through USB to an external storage device. It will only transfer data to and from a computer. He appologized and is correcting the information on their website.
Roland has tested all the older style formats from the Roland keyboards into the GW7 and they all work and now I've asked them to test the G70 styles and they will hopefully today.
George Kaye
Kaye's Music Scene
Reseda, California