I'll find out if they embellish when I can join them on a more normal ride, with more people, but that quoted speed is on the flats, not an average for the ride. My average for my commute is usually around 17, and was 17.6 for the 42 miles yesterday. But that's a computer average, which pauses the timing if you aren't moving at all (lights, flat tires, etc). On the straight/flat spots I hover in the 19-21mph range.. assuming no big head wind, of course. Any rise at all, and my speed starts dropping fast.
Oh.. and thanks.