Since the grinding wheel was obviously new with the label still in place. A data plate can be seen on top of the motor which most probably has its RPM listed. Only a moron would ignore the RPMs of the two if the one on the motor was higher than the wheel. Or this was purposely staged for either click bait or educational purposes. Which I think may have been the latter, due to the mounted positioning of the camera. In which case due to the unpredictability of when a wheel would fail it may have been drilled or struck a few times on the back side to guarantee it would shatter in a timely manner.

I wonder which was the case.