As I recall, there were quite a few schools S24 looked at that said something like they “recommended” (not required) “3-4”. The suggested interpretation of that recommendation at his feederish HS with plenty of advanced History and Social Science electives is you should probably do History/SS electives senior year, unless you had a really good and obvious reason not to.
Then most kids I know about did that, and that did not seem to stop them from getting into arbitrarily selective colleges. I am actually skeptical about “spike theory” to begin with, but I agree whatever it plausibly means, it does not mean every selective college wants you to have an unbalanced HS academic record.
But some, like Caltech, say, only requires one year each of History and Social Studies, and recommends only three total. The way we would interpret that, Caltech might be more inclined than some others to prefer additional STEM as a senior.