I don't really know, so I am only speculating, and documenting some thoughts.
There are two aspects to waster absorbtion, one is dependant on affinity for water, the other is dependant on diffusion rate.
I expect that affinity has little to do with transmission, as it only attracts water to the surface until equilibrium is established with the environment. From there, the water must diffuse through the medium. This will be partly dependant on the concentration gradient, which will in turn depend on the affinity, however if the medium is relativly impermiable, the diffusion rate will be slow, despite the concerntration gradient.
This is in fact the case with nylons. They absorb moisture onto the surface very quickly, but diffuse it through the polymer matrix very slowly.
If the diffusion rate is high, the concentration gradient will level out very quickly, and allow more water to be attracted to the surface, however if the affinity is low, very little water will be attracted, and the concentration gradient will be low, therefore the diffusion rate will still be low.
The only situations that allows for high water absorbtion rate is high affinity and fast diffusion rates, or high surface area and very thin section together with high affinity
