HIPPA is a medical thing. Coaches are not bound by HIPPA. However, if their players want it to stay private, coaches shouldn't violate that trust.Quick Google and the injury report mandate in the NFL has been around since 1947. It had nothing to do with gambling.
I'm no legal expert but I highly doubt you could bake something in to a collective bargaining agreement that forces players to disclose their exact injury.
Again just giving a status or even saying 3 to 5 weeks for example is not a HIPAA violation. Saying so and so tore their ACL without so and so giving consent is.
Illegal NFL gambling was occuring way before that as well