I think you're off by a factor of 2 or so.

An average casual biking speed in a city is about 20 km/h. So, 10 minutes would be about 3.3 km. But, most people walk a lot faster than that, Google Maps estimates about 5 km/h.

I'd say 1 hour walking is closer to being 20 minutes of biking, especially if you have to lock and unlock your bike at the start and end of your trip.