In reply to Intergalactic Planetary: I can't offer advice from a parenting perspective but I can say I've been through exactly what he has! I was climbing at a fairly similar level at his age, and climbing outside a lot more than my peers because I had climbing parents and they did not. What made it even more frustrating was that I was getting involved in competitions and getting totally beaten by people I knew I'd burn off on real rock.
A few things that helped me, or I wish I'd done -
I was similar to what your son sounds like - I could hold on for ever and I was good technically. Unfortunately indoor walls don't provide as many opportunities to use technique to trick through cruxes, so I'm afraid the only way forward is to get strong. Get him bouldering more! I used to think I was fairly strong for the grade I climbed because I could boulder well but I was bouldering well due to technique, so some real strength will see some quick easy gains.
I was also really in good at recovering at rests. Routes outside tend to have natural weaknesses which provide good rests but indoor routes are usually set to be unusually sustained. A way to work around this is to do mini shakes (a quick flick of the wrist between moves) and to climb faster. It took me a long time to realise what an amazing effect doubling your pace can have, but it's hard to learn so maybe lapping routes below his limit focussing on moving as quickly and efficiently as possible. Again this style doesn't really suit outdoor climbing, where you normally need more time to think through less obvious moves than on brightly coloured blobs.
Think of every wall session as training, and think of outdoor climbing as performing. This can be hard when you know peers are watching though as it can feel like a performance which is being judged.
I know you say 'squads' aren't his cup of tea, but for me joining the local wall team was the biggest factor. I went from 6b to 7b in a few months (and from climbing higher grades outside to climbing harder inside) just through the motivation and competition. I didn't really want to join for a long time as I found the idea quite intimidating as the rest of the team had been climbing together for ages, but once my dad had encouraged me to go to a few sessions I started to really enjoy it. So I think that's the most important one.
After a few years of climbing with the team I went from coming almost bottom to coming second in one of the BMC national competitions.
Now I'm older I do find it funny that it bothered me, as I'm sure a lot of readers will do too, and I think of it as a fun way to train for real rock. I think indoor climbing is just something that appeals more at that age, and I'm sure he'll grow out of it and find it odd too.
In the meanwhile I hope he keeps crushing on rock as it sounds like he's got a lot of potential.
Oh and one last thing! Its much easier for a weak, but technically excellent climber to improve by getting stronger, than it is for a strong climber to get better by improving technique - technique is the hardest thing to improve so your son is at a natural advantage.