This is all about runners vs non-exercisers. Again, the literature on strength training and sprint work indicates major benefits not gained from long distance running. I doubt there are any distance running health benefits compared to benefits from short distance running and/or walking.

Comparing non-exercisers to marathon runners is irrelevant. I repeat: marathons inflict measurable physiological damage. A fit person who got fit by means other than long distance running would not have this damage.

There is a much greater volume of clinical research oriented around treadmills and distance running in general because it is very easy to quantify and study. This does not by consequence recommend distance running.