At any rate, the choice to go "have a pure base" is the right one IMO: it's nice to have a system where I know I have the right to use/modify/distribute changes to the entire thing. It's easier to start with that pure base and add impurities if you need them (eg if your hardware requires blobs to operate it) than the reverse.
That said I think it would be helpful if there was a place to direct users who need to figure out how to install such blobs, even though I agree that the official mailing lists and project repository should not be it. (I am running a blobbed kernel on my current machine because I have to, but I previously was able to run with the linux-libre kernel Guix ships with. It's definitely possible to do if you need to, just not well documented.)