It would greatly impact flexibility on where to apply.
If he was ok with a U of Arizona instead of a UC Berkeley, likely no big deal.
Colleges care about GPA, Rigor, and test scores (not UC). ECs are extra…
One doesn’t need three years of language - but it will not be seen as well by higher pedigree schools.
But should that matter? He should be challenged but not strained. But he should also not have a gap in the schedule - so if you drop, maybe pick up another class.
Technically, UCs require only two years so it is possible…I assume you are targeting UCs?