In practical terms, the first point is that very few electors know the MP for their riding or speak to him or her. The person who has a health-related problem will have a tendency to address his concerns to the Minister of Health directly rather than to his MP.
The second point is that electors would have two people in their riding whom they could turn to. They could speak with the MP for the riding and to the MP from the list, or to people from the list. In that way, they would have a greater choice of people to turn to.