Yeah, there is more to this. The only reason to cut him vs. just letting him go on "vacation" is to open up the roster spot. They are paying him in either case. The Spurs don't need that spot so much, at least it doesn't seem so. You would think the best thing for the player would be to stay with the team even if not playing and have access to team and league medical/mental health services. Just abruptly cutting him doesn't make any sense.
I can't construct a scenario to explain this. Maybe he punched someone in practice, threatened a coach or something. But even with that, wouldn't most team just put him in anger management therapy?