Dudley Henriques writes:

It most certainly does work this way. If the student doesn't graduate a
good pilot, the instructor has failed. Therefore the instructor by
definition isn't the good instructor in your example.

I wasn't thinking of the graduation. After the pilot graduates, he flies. A
good pilot is someone who flies well even years after doing what is necessary
to get a license. The same applies to drivers of cars, doctors, lawyers, and
so on. It's one thing to pass a test; it's another to stay competent and/or
perhaps improve over long periods. Instructors have no control over that.