As used in RCW 72.68.031 and 72.68.032, the phrase “state institution or facility for the care of the mentally ill” shall mean any hospital, institution or facility operated and maintained by the state of Washington which has as its principal purpose the care of the mentally ill, whether such hospital, institution or facility is physically located within or outside the geographical or structural confines of a state correctional institution or facility: PROVIDED, That whether a state institution or facility for the care of the mentally ill be physically located within or outside the geographical or structural confines of a state correctional institution or facility, it shall be administered separately from the state correctional institution or facility, and in conformity with its principal purpose.