I'm not finding an explicit rule in the NCAA book like the Fed book about it, but it is implied that if B1 signals and B2 catches the kick, it is not a fair catch akin to 6-5-3 in Fed rules. 2-8-1b states that a fair catch is a catch made by a player who has made a valid signal during a free kick, implying that it must be the same player. The ball is placed at the 25 after a fair catch on a free kick, so if it is not a fair catch, the ball is next put in play where it became dead -- where B2 caught the ball after B1's signal.
AR 6-5-1-III also states that if B5 signals for a fair catch on a free kick, but then muffs the kick and recovers, the ball is placed at the spot of the recovery and not the 25 since it was not a fair catch.
I agree that it was done correctly, unless there's something else I'm missing.
Of course, all of this is irrelevant under Fed rules, since a free kick fair catch is put in play next at the spot of the fair catch, regardless of where it occurred.
I think the closest you'll find is this, you have to piece together a couple of rules:
6-5-3a: A catch after an invalid signal is not a fair catch, and the ball is dead where caught or recovered.
definition of invalid signal:
2-8-3: An invalid signal is any waving signal by a player of Team B:
a. That does not meet the requirements of Article 2.
Article 2: A valid signal is a signal given by a player of Team B who has obviously
signaled their intention by extending one hand only clearly above their head and waving that hand from side to side of their body more than once.
That's as close as there is to stating that B11 can't signal on behalf of B13 and still get the benefits of a fair catch.
On the Minnesota one, the only thing I disagreed with, was Reggie Smith saying is was the get away signal that was the invalid FC signal - he implied that all get away signals are invalid FC signals; they're not, just if you wave your arm a little higher than normal where it could be interpreted as a FC signal.