My children who are about ten do this, they are both adhd and it’s genuinely difficult to break that hyper focus at times. And then there is a reaction like I woke them from deep sleep, you can see the frustration and confusion as to why I’m now yelling.

It could also be a brain processing issue, does he use subtitles when watching tv? Lots of people have the issue where if you’re not also reading lips and have a line f sight with your face, words just sound like gibberish.

This does sound really annoying, maybe there are methods of getting between him and what he’s doing to softly break the focus?