Yeah they sold out in a handful of hours, had my chance but wasn't going to fork out 112 euro. I doubt they made the same blunder as the R-pi and grossly under estimated their release sales. Apparently the chips are new(er) and may be in high demand with little supply. Some official distributors are reporting 6 weeks to fill the orders received yesterday.
01h is a subclass of MSD ( mass storage ), Reduced Block Commands (RBC) is an interface specification.
MSD supports very basic read/write operartions (RBC/01h) all the way up to full SCSI support ( every USB storage device/06h ).
BOT is replacing CBI ( transport methods, larger throughput 'bulk' blocks ) May mean flash paging is large, but not too much of a worry.
EDIT:
AT91 USB MSD http://www.atmel.com/Images/doc6283.pdf
Universal Serial Bus Mass Storage Class: Bulk-Only Transport
http://www.usb.org/developers/devclass_docs/usbmassbulk_10.pdf