(Belated reply): I can only offer anecdotal data here, but as one of the members of GWWC, many of the members are interested. Also, listening to the directors, most of them are also interested in x-risk issues.

You are right in that GWWC isn't a charity (although it is likely to turn into one), and their recommendations are non-x-risk. The rationale for recommending charities is dependent on reliable data: and x-risk is one of those things where a robust "here's more much more likely happy singularity will be if you give to us" analysis looks very hard.