As a running enthusiast whose varied from running ~25 miles a week to having to restart from nothing, what the guy is talking about is extremely common. I’ve followed many different plans from many runners, sometimes their names are attached, sometimes not, and most of them I couldn’t tell you what they look like. I will say Olympic runners are the most common. I’ve even come across hers. Nothing about this rings as implausible to someone remotely interested in the topic. I guess I could understand from a total outsider perspective, but from someone who looks into that topic often? Absolutely plausible. I see no reason not to believe them.

Edit: the amount of stories Tony Hawk posts like this and never gets questioned also just makes me wonder a bit about why multiple people have already commented the way you did.