(a) Nothing in this article shall in any way limit or prohibit the payment of wages at more frequent intervals, or in greater amounts, or in full when or before due, but no provision of this article can in any way be contravened or set aside by a private agreement, whether written, oral, or implied.
(b) The state employer does not violate this section by authorizing employees who quit, or are discharged from, their employment with the state to take payment for any unused or accumulated vacation, annual leave, holiday leave, sick leave to which the employee is otherwise entitled due to a disability retirement, or time off to which the employee is entitled by reason of previous overtime work where compensating time off was given by the appointing power, as provided in Section 201 or 202.