Is there greater context here that helps explain what's going on? Reading the comments in the thread didn't clarify much for me as someone unfamiliar with NixOS, their apparently unique Python packaging scheme, and Home Assistant.
He just doesn't want anything of his included in nixpkgs because he doesn't want to deal with anyone opening Github issues against his repos if there happen to be build / installation issues that are coming from some kind of failure in the nixpkgs install / build process.
The nixos guys also offered various proposals to him to completely avoid any support burden on his part, all of which he roundly rejected.
Seems he's just being unreasonable for the sake of it tbh; I can't see any logical reasoning behind it all.