Pro athletes are paid to play the game, so yes if you have a game in CA, you have to pay CA taxes on that game check. I do not think pro signing bonuses are taxed anywhere but the state of residence.
Most NIL deals are for performing some other service, not the game. If you are featured in an ad, I think that income would be taxed in state of residence. If you have to perform a service in person (at a camp or corporate location), then they would likely pay taxes or report that income as earned in that state where the services were performed. Not saying states couldn't get creative, but seems like a stretch for now.
If players were ever treated as employees of the university, then the pro treatment would be right on point.