Sunfish,
I am rather surprised your friend was not shown the effects of yaw in a go-around situation with a C210. It was one of the first manouvres I had to display an adequate degree of competency at when I was first checked out on the type some years ago.
An extreme handful during the go-around, not only due to the yaw, but also the required physical push force to the yoke with full flap selected to stop the aircraft from pitching up.
In my view, it was the most important component of the check.
If he intends to purchase another C210 through insurance, I strongly suggest he attends a Cessna Pilots Association of Australia, Pilot Proficiency course that is held once a year. In the not too distant future, he and other owners may no choice to due to the direction taken by insurance companies. A very worthwhile course.
Apologies for being off topic.