I'd say it's kind of the other way around, actually. Mad Alfred has some interesting stuff, but I don't know where he really gets it from. From what I heard, the new edition of WFRP is supposed to match up with WFB. That being the case, Sudenland doesn't exist, and through revisionist history, never did. It was mentioned in the latest army book about how Solland loyalists refer to the region as Sudenland as a small measure of defiance. That is about the only way it lives on.
Perhaps Mad Alfred and others choose to use some older supplements, or other sources that are out that I have not yet seen. If so then that would work, but it doesn't really jive with what's out at the moment.