I googled this a bit today and I dont see any indication of danger to MC riders.
They also put them on the center line on some two lane roads so you dont cross into on coming traffic.
They are dips or bumps scalloped into the asphalt, and they dont have any directional component to them. Not like when they groove the pavement to put down new asphalt, or the gratings on steel deck bridges.
It might deflect your steering angle a bit but I dont think it would be enough to knock the wheels out from under you, like hitting a median or a curb. Motorcycles are incredibly stable because of the gyro forces of the spinning wheels, esp at highway speeds. It would take a tremendous force to knock a motorcycle over sideways.
Now Im going to have to find a road with rumble cuts in the center line and try it. (no officer, I have not been drinking...)