I'm pretty sure of it, and I think that Google uses Location Services on android phones to identify bike trips and flag new routes for human reviews when the "bot" sees some threshold of instances.

Around '09 or '10 I lived in an apartment complex, which was isolated except for a single road out. Way in the back, where I lived, I had a short-cut climbing up a bank, through about 30 feet of brush/forest that I eventually cleared out, to an access road leading directly a parking lot to the Greenway. After a few months my shortcut appeared as a bike route on Google Maps! I was the only one there who got around by bike (because of the killer hill on the exit road I think), so it's unlikely that some resident added it in manually as a suggestion. I am convinced that Google saw my phone moving across, day after day on obvious bike rides, and added it on that basis. I'm also pretty confident that Google has refined their algorithms since then, and bike routing is now more dynamic based on utilization.