I believe that Dr. Smith confuses irremediability of the diagnosis and the reliability of giving a diagnosis with the question of irremediability of the symptoms that lead to a request for MAID. Yes, you can reliably determine that someone has schizophrenia or suffers from depression, but the vast majority of people with those mental illnesses will not seriously consider suicide, request MAID or have severe, untreated symptoms that lead them to want to die.
I'm a scientist. The latest Cochrane Review of research on the ability to find some indicator of the future course of a mental illness, either treated or untreated, concluded that we have no specific scientific ways of doing this. We are relying on the clinical hunch of someone who hasn't known the person for 20 or 30 years and who has no scientific data showing that they can determine this.
I accept that many mental illnesses are not remediable, but that doesn't mean that a person with proper treatment will not have a good and full life, despite the fact of having a mental illness. The real issue is that, in suicide prevention, every single person who calls a crisis line meets the MAID criteria. They are suffering. They feel it's interminable, and they often have refused treatment.
The difference between Canada and every other country in the world is that elsewhere in the world, if the physicians feel there is a treatment, the person doesn't have to do the treatment. It's up to them, but they don't kill them.