Not sure if this is relevant, as DD did not apply to tech-focused schools like the ones your son is looking at, but she didn’t encounter any schools that had a problem with her SAT2s done at the end of freshman year and sophomore year.
I think if he is applying to a specific program I would contact them and ask directly. It sounds like they might use them for placement, which seems a bit strange. Most places DD looked used AP scores and their own internal placement exams for math, sciences and foreign language. The only time anyone cared about an SAT 2 result was a freshman honors science class DD applied for, where it was part of the data they asked about (though there was still a departmental placement exam for that as well).
I know some kids do repeat SAT2s, though usually just to improve the score- it’s do-able, but it would certainly be frustrating.
