FossilNF, my DS has been swimming competitively since the age of 9. He sounds similar to your DS in that he trained really well and kept up in the competitive squad against all of the top swimmers. However, when it came to racing, his times weren't anywhere near as good. He generally achieved County CT times whereas they were achieving Qualifying times. Obviously, as he got older, her started to become pretty frustrated and stressed out by it.
Last year, he only achieved (I say only as this is a highly competitive club) one Regional time and was moved into the less competitive squad. The slightly more relaxed attitude has been a huge boost to his confidence. A couple of times a week he swims with the competitive squad and still complains they mess around. However, guess what? Last weekend he swum at Counties and achieved 2 fantastic PBs and actually beat a couple of the so called Top swimmers! In the last 6 months, DS has had a massive growth spurt and is far stronger and more confident.
I actually think at their age a lot of it is to do with their body shape and strength. Right now your DS will be focusing on technique, whereas, for a lot of the other swimmers they rely on strength and speed to win races. In the long term your DS will be far better off. As he matures, his strength for racing will come and his technique will be far better than those who mess around now and rely on strength in races.
I hope I've made a bit of sense here!!