Not really true since motorcycles are covered by all the rules in California that mention "motor vehicles" in addition to those which apply only to "vehicles." In addition, California explicitly excludes bicycles from their definition of vehicle but instead considers them to be human-powered devices, although bicycle riders are assigned the same rights and responsibilities as vehicle operators except for specific exceptions.

The only type of flashing light that's specified as illegal on a bicycle in Calif. is a blue one since that color is reserved for emergency vehicles. But bicycles operated at night are required to have at least a red reflector on the back (plus pedal or ankle and side reflectors) and a white light on the front that illuminates the road as well as providing visibility from a distance. Having only a flashing light (esp. with a slow flash rate) could be interpreted as not satisfying the road illumination requirement if you meet a particularly picky officer, but I doubt that you'd get cited as long as you're willing to switch it to the steady-on mode.

A tail light (either flashing or steady) is not required by the Calif. vehicle code, but is certainly a good idea.