"Probably" is being used here because the body doesn't have a really good way to rebuild cartilage, especially as you age, due to lack of blood flow into places like the patella. Knee and hip replacements are on the rise (
https://oip.com/the-lowdown-on-the-uprise-of-knee-and-hip-re...) as well in Boomers, indicating that age related degeneration (with or wihtout a history of running) is fairly universal and expected.
There's absolutely some perfect middle ground of "just enough" running that will strengthen, but not deteriorate too quickly, your knees - but again where that point is will vary by individual. It also may not be something that can be determined except in hindsight, partly because medical professionals generally don't start monitoring cartilage until the person is reporting pain or mobility issues (or a known condition they're checking for symptoms of).
Point being that statistically there are useful trends in aggregate data that can be observed, but, paradoxically, those trends don't necessarily translate to good general medical guidance. One counterexample where those trends do translate would be something like that peanut allergy study from 2015 that was linked on HN recently about introducing allergens earlier and frequently to babies, resulting in fewer teen/adult allergies.