Yeah, that was me. Both times that I've hurt my right knee, I'm fairly sure it's been that exact same motion... The first time I was coming down on my second backroll attempt and underrotated some, so I'm not entirely sure how that went down, as at the time I didn't really feel completely aware as to the whole thing...
At times though, I think people may blow out their knees just by landing too stiff legged. There were two blowouts in The Truth (I think), Daniel Doud (is the possible one, he's shown with ice on his knee...), and Collin Harrington's. Neither falls looked like ours did, however, I think the outward/inward pressure put on their knees when they were landing is what did it to them.
I'd say that you're right that there are plenty of knee injuries from doing what we did, but I'd also say that there are a LOT more contributing factors, as I've landed like that dozens of times in the season before this and hadn't had any problems.