I think the article is valid, if all other things are equal. The arguments alone don't really hold. If it was a simple matter of having more skin to dissipate heat, then it would reason that large people would be more efficient runners. But as someone already pointed out, larger = more mass = more work.

I'm above average height for a female (5'7"), but I have relatively short lower legs. (And I have a hard time with running). Like Emily, I seem to have long femurs for my height. DH is 6'5", is an average runner, below average swimmer, and above average cyclist. He has pretty long lower legs, but he weighs 204 which is just a lot of mass to move.

It would be interesting if the study looked more at the proportion of lower leg to upper leg (and to overall height). . . .