I had the same thought. Their stated goals are very much in line with what nix is all about.
Sadly, I totally get why they didn't. The nix way still isn't ready for "hey everybody, I'm making a thing, let's work on it together."
The hurdles are just too high for non-nix-nerds to pick it up while simultaneously trying to learn the underlying project.
It's a better way, currently only for those primarily in search of a better way.