There is no disagreement there. Reproducibility is definitely a goal though.

I don't really understand your line of argument.

It's a goal but not a fundamental design requirement for nix packages. It seemed like you were implying that you had to make nix builds reproducible in order to get them working with nixpkgs, which wluld greatly complicate things.

Yeah, if every language had their build systems in order, we wouldn't have needed nix as much, so definitely grateful for what nix does. But some problems can only be elegantly solved a level below nix.