It doesn't really make sense to compare that effort to a race of any kind, let alone a mountain bike race -- since the thru-hikers we're talking about were not doing it as a race. Of course their effort was done at a lower level of intensity. For some perspective, a fellow recently set the Colorado Trail record with a time of 9 days 12 hours, almost three times as fast as the thru-hikers in the article: http://johnzahorian.com/coloradotrailfkt
For anyone interested, here's a youtube video documenting the record effort. The guy is kind of a celebrity in hiking circles, in large part because of high-quality videos he makes of his adventures:
https://www.youtube.com/watch?v=Vk6CrWJdRto
(Zahorian's effort set the "unsupported" record, which means he carried everything, including all his food, from the start, and didn't stop at any towns along the way to resupply. Most hikers carry only enough food for 3 to 5 days at a time, and resupply along the way -- understandable because it's much easier than carrying everything from the start.)