All persons employed in reduced worktime positions for partial service retirement pursuant to this article, shall receive proportionally reduced compensation and, on a pro rata basis, except for benefits provided under the Public Employees’ Medical and Hospital Care Act, the State Employees’ Dental Care Act, and the California Dental Service program, all benefits customarily available to full-time employees of state agencies in similar classes or positions. With regard to benefits provided under the Public Employees’ Medical and Hospital Care Act, persons employed in reduced worktime positions for partial service retirement shall receive the same benefits as are provided by law for employees under the same circumstances who are employed, full time. The department may, for purposes of administrative efficiency, treat the class of partially retired employees as fully employed with respect to health care benefits, provided that such administrative treatment does not impair the level of benefits to which the class would be entitled if treated administratively another way.