the yankees have a switch thrower in their minor league system. maybe soon all pitchers all switch throwers.
I believe doing both sides is good for athleticsm and health. there are also theories that the "good side" learns also when you use the weak side. so it's a good coordination training.
but the biggest reason for doing it a little is health. rotational movements only done in one direction are know to be very bad for hips and spine because of the asymmetric load. thus many sports scientists recommend to do rotational movements in both directions to allow for a more balanced muscle build up (so that not some muscles become to short and strong and others too long and weak).
but I think for most kids the actual chance of using this in games is small. I would still do it if he likes it. not half of the practice times but a couple of minutes a day.
I think walks are overrated unless you can run. If you get a walk and put the pitcher in a stretch, that helps, but the guy who walks and can’t run, most of the time he’s clogging up the bases for somebody who can run. – Dusty Baker.