This thread is an eye opener as I'm so not like any of you.
I'm an old guy, but I weigh 138 and can hit 200 watts for 20 minutes (nothing to brag about, but still more than several here have mentioned)
My 190s output for 1:15 was only good enough to land me slightly above mid pack for my age group in a 11 mile 3200 ft climb fest.

So at lighter with more power than many posters, I am only OK as a climber. Well, really, only approaching OK.

AND I can't hit more than low 20s (OK, maybe mid 20s) on a sprint, and the idea or rolling at 20 for more than a mile without a tail wind and a downhill? Impossible.

My point:
I can only conclude that these flat land speed estimates are grossly inflated, or that I have the worst aerodynamics on the planet. I'm guessing the former.

EDIT:
What hhnngg1 said