I don't see a problem with it.
Even the McD example. McD went to UNI and coached at UNI. If
ISU was done for the season and UNI wasn't and McD wanted to support UNI, I wouldn't have a problem with it. It is his Alma Mater.
Now, if
ISU LOST in the tournament to UNI, I might be annoyed but I still think it is all in good sportsmanship.