How are deterministic builds better than distributing binaries with hashes for verification? Just because I don't have to trust the original author's compiler?
Indeed, that's precisely why it's such an important protection mechanism. But it's about more than just not having to trust the original author's compiler. The original author might maliciously copy-paste some additional source code into the build process just before compilation.
Deterministic builds are a way for any of us to download any source code, build it, and verify that all of us are using a binary derived from exactly that source code, and nothing else.