This is not a strong statement. This is, in fact, a well-known framing of the problem. It is often virtually impossible in clinical practice to distinguish between the symptom of suicide and the death wish expressed in the form of a euthanasia request.
The International Association for Suicide Prevention has attempted to come up with a statement trying to guide clinicians to distinguish between a death wish as a symptom of mental illness and a death wish as a rational expression of euthanasia. In theory they may exist, but in clinical practice they are very difficult to distinguish from each other.
Therefore, what often happens is that individuals indeed suffer and express a death wish as a result of their mental suffering which results from a mental disorder. They are granted euthanasia, so the doctor performs the suicide. This is not a strong statement. This is an internationally accepted framing of the question before us.