Yes, at any of the UCs where he was admitted, he would have likely taken the credits for his math courses during HS.
In fact, I’m not actually sure he would have had a choice, since all those math courses were on transcripts he would have had to submit from a couple community colleges and UCSB. And, the assist.org website is pretty clear about how those courses should transfer, whereas one might have more choice about whether to take AP credits.
Which is why I say, “It depends.”