“a member institution may comment publicly only to the extent of confirming its recruitment of the prospect”
I think the posting in laxpower by the coach/school would fall under this allowable act, that the school is confirming its recruitment of the prospect. Everyone knows the school or the athlete can make another choice until the signing, or even after signing if the student isn’t admitted academically to the school. As for why kids would post it early? Bragging, relief, making it real, to be the first (my daughter was unhappy when a rival committed first). There is a huge amount of pressure to get a spot at a top school before they are all gone. Everyone at the recruiting tournaments wants to know if you have committed, where you are going, who else is going to that school. Some parents ask all the time, some are sharing tips on how to get recruited, how much money you can ask for, etc. I not only check my daughter’s team for who is coming and which position she plays, but the recruiting classes of the arch enemies, the other schools in her conference. I look for old teammates to see where they are headed.
To be fair, most of those contacting my daughter after signing were D3 schools, and she was free to go, and play immediately, to any of those schools. If a D2 or D1 school contacted her after she signed, it was inadvertent and they quickly backed off. Until signing (and many kids wear pink arm bands before signing, some as early as their sophomore year), it’s open season and the schools all keep calling.