All that is known is 1. One individual has a new firmware on their camera (there are many buying Mark III's at the moment who aren't getting it), and 2. It doesn't allow roll-back. Additionally, since it references TWO unheard of firmware versions (1.3.0 AND 1.3.3), I'm inclined to think this individual might have received a developer test unit somehow. Based on that data, I would've gone with the title "New 5d Mark III Firmware?" instead of your impulsive "Canon blocking Magic Lantern." Just a tip if you'd like to be more objective and avoid jumping to conclusions - a prerequisite of being considered "news."