We do a lot of off-hand freestyle drilling but I tend to punch so that the student gets hit if he/she doesn't take an angle. In this drill it seems like the student allows himself to be tagged and then deals with the offending hand after the fact.
HOWEVER...
I intend to watch this when I get home from work with the volume on.
Sifu Cheung is one of the few sifus on youtube that I will listen to very carefully. I believe he has an alarming prowess of the internal elements of the art. Although I've met him, I haven't rolled with him but I have rolled with some instructors who have learned under him. They were impressive.