So I went to my local Cabela's to check these out. I had been wondering what 'whipcord' was, and it turned out I knew all along and I even already have a pair of pants made out of it. 'whipcord' is basically the finest possible steelwool.
The pants (and shirts) at my local Cabela's were the previous version to the one linked in the OP, 24 oz fabric rather than 18 oz. So for my ownself I got 2 pieces of info out of the trip: what the fabric was, and what waistsize to order (the comments on sizing at cabelas.com are confusing at best).
Anyway, I did order a pair but not for biking even the 18 oz would be way to heavy for me, but I do have other uses for that kind of thing.
If someone was more budget conscious it would probably be better to scope military surplus for E German or Swiss handmedowns, that kind of thing, and if fabric-weight-specific, go the thriftstore dress pants route.