Typically, "recommended " means required unless you have a compelling reason for not submitting. (And this may relate to being in a targeted population.) So yes, they probably want them. Can you not submit? Sure. I would say this is a strategy that might work if your kid is in the relatively small group that simply need nothing wrong with their applications (like children a major donors or highly recruited athletes. ) That group is “in” as long as they don’t trigger a no from admissions and, unfortunately, isn’t most of us.
There are schools that don’t require subject tests with the ACT so that path is an option at those but you will need to go through your list school by school to see if/where that applies. The ACT is, imo, an easier test to improve on if you invest the time in figuring out how to work quickly. So if your S did not prep a lot, pulling that score up for those schools is possible and could help. But if he’s burnt out and not up for that, I would simply adjust expectations accordingly. He will certainly have good options with what he has, including his music, just perhaps not a pile of tippy tops. At some level, he’s telling you he really doesn’t feel like killing himself to feed that kind of ambition. Nothing wrong with that so long as he’s not delusional about it.