I wouldn't get too caught up in his playing time as a freshman. Many times, coaches have preconceived values of players, there are growth/maturity factors, next up for Varsity, etc. Freshman year is typically a waste of time, outside of a few either talented, or early maturers. This all typically shakes out over a 4 year HS career.
Focus on summer, having your son regain his love for the game. His role should grow with the HS team, if his talent and dedication are there. It's a journey, some kids don't get meaningful time until their senior years, if they even do at all.
Maybe also write down the goals for your son. Is it to be a starter 100% of the time and do his talents match that? Is there value in just being part of a team and bonding with his HS peers for 4 years? Do you want him to have the structure and challenges of being a student athlete, regardless of PT?
I know playing time can be frustrating. I haven't had that with my son's pitching, but he was forced to be a PO as a sophomore. I used to struggle with him sitting on non-pitching days, as he's a good athlete and can contribute offensively. But being a pitcher has buttered his bread, he's OK with being a PO, as am I. I still go to games when he's not pitching and cheer for the team and watch him have a hell of a time in the dugout. Heck, it's a lot less stressful that way too!