Notwithstanding the definition of "employee" in RCW 41.59.020, the commission may exclude from the coverage of chapter 288, Laws of 1975 1st ex. sess. any specialized job category of an employer where a majority of the persons employed in that job category consists of classified employees. At such time as a majority of such employees are certificated, the job category may be considered an appropriate unit under chapter 288, Laws of 1975 1st ex. sess.