What I don't understand is why the Spurs seem to think that their players need to play heavy minutes as focal points to learn. Being the clear best player on a team has advantages and disadvantages. Primo will very likely not be the best player on the Spurs when/if he gets a regular role with them. So a lot of time he's going to spend isn't really going to be used and may never really end up being helpful. It's much harder to learn things like moving off the ball and the timing of catch-and-shoot jumpers if you're always dominating the ball, and I think that is evident in how the young Spurs have played.
Funnily enough, one of the more noted Spurs development attributions, Danny Green, got most of his d-league burn with RGV where he wasn't asked to be the main ball-handler and got to play off Jeremy Lin instead. That allowed him to work on actual NBA skills. When he came to the Spurs, Pop tried to play Green at point, and that obviously didn't work. Danny had a lot of rudimentary skills like off-dribble pull-ups and slashes that never really became part of his game. If he'd spent a year focusing on those things rather than on refining what he did well into an NBA-level skill-set, then he'd've probably been out of the league a decade ago.
In that same way, I think if Murray had focused on shooting threes early in his career, he'd be a highly coveted three-and-D player like Green or Covington who was also starting to break out a floor game that suggested a higher ceiling rather than a guard whose offensive impact doesn't match his eye-test skills. That's not all on the coaches, as I think Murray's temperament made him predisposed to this style of play, but given how the team has approached developing all of their other prospects, I don't think he had to try very hard to convince them to put him on a star development track in lieu of role-playing 101.
I like Primo and think he has potential to be an offensive focal point. But I don't think he needs to train to be one now in order to get on the floor. He already seems to have an NBA body, an adequate BBIQ and skills that can make him useful on the floor. I think he could be a plus for the team right away, even though I am not one who considers him a clear star. My point is that even in fewer minutes, playing real games in a role he'll be playing with his actual teammates will do more to make Primo a contributor than would learning skills he's either going to have to shelve when he plays in real games or have them conflict with those of his teammates. Otherwise, there's a legit chance that next year, Josh is yet another guy running around the team without a sense of flow who makes flashy plays but gunks up the offense with poor spacing and awareness. And whichever guard the team drafts next year will be in the d-league while folks here defend it by saying that guard "needs to play heavy minutes as a ball-handler to grow and won't get those minutes with the big club".