Correct. To my knowledge, there is no legal way to possess a suppressor or high capacity magazine in California, under their current laws. In (almost) all other states, high capacity magazines are not regulated, and suppressors can be legally obtained with a $200 tax stamp and NFA form.
I'm not from California, so I'm not as familiar with their laws, but I find the idea of an easy loophole to suppressor ownership very difficult to believe.