Biking is also pretty dependent on the individual and their setup. The elevation changes, distances, sustained speed, and terrain one individual and their equipment can handle can vary drastically with another person. Not to mention someone’s tolerance for whatever the weather might be doing at the time while you’re completely exposed to the elements on a bike or walking.
It’s just them taking a “your results may vary” approach while covering their own ass.
Anecdotally, while driving in Colorado, I put in a destination that I was driving to in bike mode on accident. The destination was like 80 miles away from where I was and involved climbing and descending a mountain pass. Google Maps was very optimistic about how long it would take me to bike there…all without knowing my anything about my health, the kind of bike I have, if I would be able to bike at that elevation, etc. (being Google they probably knew)