There are some "sprinty" swimming events he could do I guess - the 50m and 100m swimming events happen in under a minute. But it would be harder for him to train (Mom's not going to let him put in a pool, the garage gym is bad enough) and he couldn't let power substitute for skill to the same degree as in cycling. I think he's already in the perfect sport for his abilities and inclinations.
The thing with swimming is that the chances of a LoL moment are very limited. Diving could provide a slip on the board and a massive belly flop, but that is about it. Track cycling gives us the possibility of seeing one of a variety of destroyed in 60 seconds moments. As long as nobody else gets hurt, of course.
It is pretty safe compared to say, eventing on horses, but fucking hell when it goes wrong it goes wrong big time. I know a couple of people who will never walk again due to spinal injuries from velodrome crashes.
Do some digging on the net and you will find the chap who had the enormous splinter of wood, from the track, through his leg. Also the accident in belgium, maybe 1-2 years ago, where 2 bikes and 2 riders ended up in the crowd, at the top of the banking ffs!!
Then there is the british rider who was very lucky to not die from internal injuries and had her spine exposed, post crash......pass the bucket please! and there is the south american girl who plowed into the starting gate that had not been removed in time, during a team sprint( (i think that was pan-american games or something like that- deffo on the tube). Most well known, from recent times, is Kristina Vogel who plowed into another rider during training. She not be walking again, sadly.
Those are the biggies from the last few years. In the old days it was way worse. Two events in particular were real killers and they were motor paced(bear in mind the early powered pacing bikes back in Major Taylors day were steam powered, so added risk there) and 'stayer' racing. The latter is absolutely bonkers and you will find some 70's-80's footage on the tube which is worth a watch.
It is basically big engined bikes, like a Harley, looning around with the rider standing up to create a foil for the cyclist, behind. I believe the only big engine stayer events running now are very occaisionally in belgium. A real crowd pleaser (the old days saw them doing 60-70mph as the bicycles have enormous gears)and it is the only time biker gangs and lycra mix!.
These days the motor paced stuff is behind little two stroke moped things with fat riders, called a Derny. Still good for 40+mph with a cult following and still a spectacle.