I know an ultrarunner in my state who is over 65, has had 1 hip replacement, and is currently running about 140 miles a week in preparation for a summer race. So this type of thing is not unheard of.
This runner told me about it recently and I don't remember all the details, but he gives most of the credit to his doctor. He said that his doctor checks in with him frequently for updates and uses his case as a research case-study, or whatnot. I believe this runner also told me he may likely have to get his other hip replaced in due time, but I don't remember for sure. I don't remember the specific reason for having to have the replacement.
His doctor has tracked how many movements (ie. steps) the hip has made (somewhere in the millions), and other data. It's a unique case and you might call it crazy...but it's true. And he is still going strong. So good for Dave Whiteside.
Cheers. Also u/Wet Coast you make some good points.