That rule has existed since a harmful rumor started on CougarBoard caused Aaron Francisco to be woken up early in the morning. It actually happened more than once; I can't find the first time, but here was the second:
https://www.cougarboard.com/board/message.html?id=397949

You'll see that was well before NIL. There have been other incidents with outgoing transfer rumors that have caused harm, which is why we don't allow them (we do allow incoming transfer rumors). About a decade ago, I made a commitment to the athletic department that CougarBoard would not be allowed to be the source of such rumors.

The whole "rumors locked behind paywalls" thing has happened on and off over time. See this from the same time period (over two decades ago):
https://www.cougarboard.com/board/message.html?id=372128

My point is, whether NIL has hurt college sports (I agree that it has), nothing you've mentioned really has to do with NIL.