Zstd for example only promises determinism on the same version of the library. I've personally seen the hashes mutate between pull and export. Things like tar padding also make a difference. Really, the thing to do is to hash on the _uncompressed_ data and let compression be a transport/registry detail. That's what I've done, at least.

I didn't know that about zstd, that's a bit unfortunate.

Tar isn't related here though, we're talking about compression not archival formats