I don't know if it ended up implemented, but there was talk of patching Linux to re-enable the necessary symbols for ZFS. This would let it use SIMD again, and

I don't know if it ended up implemented, but there was talk of patching Linux to re-enable the necessary symbols for ZFS. This would let it use SIMD again, and speed it up to where encryption isn't a performance hog. It'd explain why you get different results on NixOS. EDIT: Seems like it was, but has been removed as unnecessary on newer ZFS versions.