For purposes of eligibility for medical assistance under chapter
74.09 RCW, minors in inpatient mental health or inpatient substance use disorder treatment shall be considered to be part of their parent's or legal guardian's household, unless the minor has been assessed by the authority or its designee as likely to require such treatment for at least ninety consecutive days, or is in out-of-home care in accordance with chapter
13.34 RCW, or the parents are found to not be exercising responsibility for care and control of the minor. Payment for such care by the authority shall be made only in accordance with rules, guidelines, and clinical criteria applicable to inpatient treatment of minors established by the authority.