I think this has to do with flakes. If you run something as a flake it doesnt use channels, which is the alternative. The import is looking for it as a channel on the host machine. With flakes its provided as an input.
It looks like nixinfo is explicitly looking for channels to tell you info, like how neofetch would tell you interesting stats. The same does not apply with flakes. There's no "default" upstream package base that can queried by the system.