Why?! I guess the rounded rungs have some benefit if that site is selling them? A broom handle seems a good diameter and you can get broom handles for £1 a pop on t'internet!
I've been thinking about campusing and deadhanging recently but don't want to fork out loads on branded campus rungs. I can't really be assed to try and sand the edges of square bits of wood as I've tried this in the past and the results were disappointing to say the least.