Oftentimes it's not even that, or can go to the opposite extreme. It can be "or until evaluated by a psychiatrist or MHP".
I'm a paramedic in Washington. The biggest example of this I remember was a 14yo, intentional pharma overdose. We brought her in, "invol". Four and a half hours later, call goes out, same address, 14 year old girl, overdose. We checked with dispatch, was there a glitch?
Nope. Psychiatrist had spoken to her, determined she was "no threat to herself". Parents drove her home, and within fifteen minutes she'd locked herself in the bathroom again, and taken more of the same meds.
Was furious. Between the psychiatrist, parents not locking up the meds, hell, the ER, she probably still had drugs in her system.
"Maybe hold on to her for more than four hours this time."
Also, tangentially, if EMS wants to transport you involuntarily, we actually need Law Enforcement involvement - they don't even necessarily need to talk to the patient, but they do need to complete the paperwork that takes them into custody, which they then "assign" to us. EMS generally has no power to treat you against your will (however, if you are actively a threat to yourself, we can act on that, usually restraint and sedation. Or there is 'implied consent' where if you lose the ability to effectively consent, the law assumes that a rational person would want aid to be rendered).