Or cyclists like to shave their legs and want an excuse? Or shaved legs gives a psychological boost (more committed), is better for injuries, or when getting physio/massages; or a combination.

Edit:

It's curious to me, because in other areas it seems some degree of surface detail reduces drag (golf balls, aeroplanes too I've heard) - I wonder if short stubble is actually better and that's the effect you get using real legs. That would account for a plastic model only having a small gain.

I don't think this example generalises quite to that conclusion: as the tests show, the differences are huge, having bigger advantages than getting top-of-the-line bike equipment.

Assuming that we're already reaching the tail-end of the bell curve for human performance in cycling sport (which seems likely to me), suggesting minimal individual performance differences, then being at among that group despite a 7% performance disadvantage seems downright impossible.

So especially at the top there would be an incredible selection against anyone with hairy legs.

But I guess you could say that natural selection beats human belief.