His injury may or may not be down to running shoes but getting the right pair from an early age will stand him in good stead when he gets older.
I’m just a layman but the wet foot test is a good initial indicator whether he needs neutral or support trainers
https://www.sportsshoes.com/support/running_articles/
And like you say guys in running shops will know which shoes will suit him
Everyone’s different but I find that if I use normal trainers when boxing they grip too much and as your foot pivots it meets resistance and I’m sure that gave me wear n tear problems on my Achilles. If I’m indoors on a bag or in the ring I’ll use boxing shoes but if I’m in my garage on the bag I’ll just use an old pair of trainers where the tread has worn away.