It's more complicated that just good or bad, Rojo.
Lot's of reasons to have reasonable limits on endurance work.
Whether it is volume or intensity of work, you're still talking about hazards and cost / benefits.
The net benefit of exercise is undisputed ; moreover there are numerous confounding variables around heart health. Calcification can arise from deficiency of vitamin D for example (a likely factor with runners in low sunlight, northern climates such as the Netherlands). Another consideration is magnesium deficiency, also linked to calcification in the heart. Potassium is a key protective mineral as well. Strong evidence for a protective effect of plant-based eating too. So you really have to look with soft eyes at these data and try to sort the bigger picture.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5841863/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4315380/