Dunking in college basketball was outlawed from 1967-68 through 1975-76 as an illegal shot. So the game against Michigan would have been been one of the last played where you couldn't dunk.
I have the coaches film of that game, and it kind of skips around and doesn't contain all of the action and that portion of the game must not be included. But if you look at about the 0:17 mark of this clip:
https://www.youtube.com/watch?v=Fz1FO7ImIFQ
you can see Kim Anderson dunking on a fast break and it certainly looks like the official rules the basket good and calls it an and-one. That is actually right at the beginning of the game, but is that possibly the play in question? And if not, then why was that play allowed and the later dunk called a technical?
Appreciate any clarification from anyone who can recall, that was before my time.