First off, the UM guy was on the sidelines. Literally snuck down there in CMU apparel when they were playing Michigan State. That’s above and beyond “just attending games.” You’re obviously going to be able to get a much better view of the signs from there. He could have likely walked around to the MSU sideline if he wanted (and maybe did).
Secondly, its pretty cut and dry that in-person scouting of future opponents is expressly illegal in the NCAA rulebook. Been that way since 1994.
And there’s a ton of evidence that Michigan has pushed the envelope much farther than anyone else in that regard, based on actual results on the field. They were world-beaters all during the regular season last year, then sh*t the bed against a vastly inferior opponent in the CFP who they very likely didn’t have on their future opponent bingo card. They’ve been 8-4 or better every year of the Harbaugh era, except for a putrid 2-4 record in 2020, when, guess what, nobody was allowed to attend games. Hmmm….