California considers 40 hours per week as full time employment. See California Labor Code Section 515 (c): "For the purposes of this section, "full-time employment" means employment in which an employee is employed for 40 hours per week."
The section referred to is used to compute "overtime pay."
California law defines full time hours for purposes of calculating overtime pay only. With respect to benefits, that is determined by your individual employer. Your employer is not required to offer any benefits at all (at least for the time being) and can choose the terms on which benefits are offered as part of your compensation package.