[bt1a]

i thought it mainly implied architectural/hardware compatibility and deterministic output

[aidenn0]

Nix mostly does not guarantee deterministic output. It rather guarantees deterministic inputs, and then sandboxes the system to inhibit the build from accessing the outside world.

Deterministic inputs do not always imply deterministic outputs.

[pabs3]

Indeed, the Reproducible Builds community is working on fixing non-deterministic build output https://reproducible-builds.org/