I think what you're describing is still the case, but the way you described it isn't quite accuratie. The default kernel used is linux-libre. If you need more hardware support and binary blobs, you use regular linux, the same one basically all the other distros use. You're not using an unofficial fork of anything (or some might argue the default is more of an unofficial fork). You do have to go out of your way somewhat to get the standard linux instead of linux-libre, and I don't believe you can just load your required firmware into linux-libre instead. It's one of the FSF-approved distros so there are indeed strict guidelines (FSDG) on proprietary software, often to the point that it puts people off, and the official IRC and probably the mailing list as well don't talk about the non-free bits, yes. However if you join the #nonguix IRC channel or use the guix channel (like a repo or PPA) of the same name you'll find many of the same faces from the core community there. It's just a bit hush-hush due to the guidelines. Remember Guix System is a step more extreme than Debian, so even something like Debian's official non-free repo is not allowed.
Personally I have run Guix System on a ThinkPad X220T and ThinkPad T440p which are old enough to not really need any blobs aside from the ones for WiFi, and you can remove or replace the card in them. I believe any machine newer than this is going to need blobs for the integrated graphics or other things. I have been debating whether I'd run Guix System on my next (newer) machine and as I've never gotten too deep into the weeds understanding Guix stuff despite using it for years, I may opt for a different distro, but I would say if you really want to try it, it's probably not too bad to get up and running with a regular non-libre Linux on Guix System.