"Is there some other factor that drives the minimum kerf for a particular riving knife?"
I suspect that it's mostly corporate paranoia…there's always a chance of incompetence too! ;-) As long as the blade is at least as wide as the riving knife, you should be fine. Wider is ok to a point, but a blade that's thinner than the riving knife will cause a problem with binding. 2.2mm = 0.0866142". Most 10" thin kerf blades are in the range of 3/32" (0.09375"), and will work just fine…..add a smidge of runout to every blade and every saw and you've still got some wiggle room, so even a blade with a kerf of 0.090" should be fine, which is about as thin as most traditional 10" TK blades get. Be sure the blade, fence, and riving knife are all well aligned. Avoid the ultra TKs and smaller diameter blades with smaller kerf, and you'll be good to go.