I grew up in the area and competed against Santa Monica before. Granted, it's been a few years, but I don't remember them ever having a JV team.
I also don't see any JV standards on the link the OP posted, so this would imply that anyone can run JV regardless of their times. But I do see frosh-soph standards that appear to be quite strict. A freshman running a 12.6 100 would be off the team, but a senior running a 13.6 would be on it. That makes no sense.
The other long-shot possibility is that the freshman running 12.6 would run JV. But I've never seen that at any school that I know of. Freshmen are either on varsity, in frosh-soph, or not on the team. Only juniors and seniors can run JV.