I think releases are school specific-meaning if XYX College wants to talk to your son, they must get a release specific to them, and if another school wants to talk to him,they must do likewise.
Once he decides to go, there's no turning back. And be very careful to tell the existing coach first thing. Nothing worse than a friend talking to a coach at another school, who in turns calls the current head coach, who knows nothing and says "Oh really???". It happened to a friend's son, and it got real ugly, real quick. The baseball grapevine is legendary and once a few conversations happen, it'll get back to the current school lightning fast.
My son went to his head coach first, and the coach was so impressed that he did so that he even called coaches at two schools where my son was interested in going and gave glowing recommendations, and my son is at his first transfer choice now and loving life.