Yes. I edited out the reference to the instructor, because it seemed to draw unfair criticism of an otherwise excellent instructor. He was quite able to discuss C172 fuel system in detail. However, he is new to the flight school and to this (still unexplained) edition to the school supplied pre-flight check list. He also asked the all other flight instructors and interestingly none of them knew the reason for the addition either.
I have found all the posts quite interesting, but I've concluded that cycling the fuel selector valve may simply be to prevent it from seizing up as a result of being left on "Both" all the time.
I do know that the senior mechanic has had many years experience maintaining a fleet of c150's, C152's and C172's for this particular flight school.