Isn't this just California being in the "3.6 roentgen, not great, not terrible" phase? I.e. number of new cases reported is limited by the number of tests that are able to be made?
Every region (and almost every country) is generally believed to be severely undercounting cases because of limited testing. There's not much reason to believe the problem is worse in California than elsewhere, and a severe surge would be evident in hospitalization and death rates no matter how bad testing is.