Yes, it's a matter of interpretation. The third party must initiate the request, as was previously mentioned. The physician must then determine whether it's valid and will then examine what the patient has written.
The cited criteria are often incontinence and inability to recognize family. However, those criteria may emerge early in the development of the dementia, but the person may nevertheless be happy. Some people don't want to use the term "dementia" because they consider it so pejorative. That shows you how much "dementiaphobia" there is in society.
My colleague mentioned the discomfort that may be felt at the idea of suggesting medical assistance in dying and the fact that we sometimes prefer to wait for the patient to request it. When one of my patients has an infection, I don't wait for him to ask me for antibiotics; I know that they're the appropriate treatment and therefore suggest it. The patient may then decide whether to accept it. When I know that a treatment is right, I propose it without waiting to be asked.
It's interesting to note this discomfort over medical assistance in dying. If physicians wait for patients to request it from them, that may be because they aren't comfortable proposing it. The discomfort may also be exacerbated by "dementiaphobia". The word "dementia" is so frightening that some people in the United States have decided to call it a "major neurocognitive disorder". The stigmatization associated with dementia is known and present.
When an individual reaches an advanced stage of dementia and the medical team attempts to determine whether the patient's inability to recognize his or her loved ones constitutes sufficient suffering to warrant medical assistance in dying, they may potentially be relying on "dementiaphobic" criteria.