I'm gonna say it's normal enough. The 4 studs that bolt to your sprocket aren't threaded into the sprocket carrier like some bikes have, these just slide into steel lined rubber bushings, they're just there to transmit torque from the sprocket to the hub. What really keeps the sprocket on the hub is a big washer and a big snap ring. I freaked out a year or two ago (before I knew all this) when I was running my CM400 in gear on the center stand, I could see the sprocket carrier wiggle and wag when I'd rev it up and let it settle down. I later read on the SOHC/4 forums from one of the old timers there that knew mostly everything on two wheels (lots of know how there too) that it was pretty normal, scary if you don't expect it, but normal enough not to worry about as long as the sprocket spins true without wobble or hop when you spin the wheel.
Wow I guess you got your answer while I was typing my reply, good group we have here.