Yes, it is. We used a minimal patch from OpenSSH upstream on stable branches rather than upgrading to a version with potentially‐breaking changes, so it’s expected that the version number doesn’t change.
Maybe we should have tweaked the derivation name or something so it’s easy to tell if you have the fix. Other people probably have smarter ideas than I do for checking you have the right version; there’s nix derivation show at a pinch, and you can check the nixos-version --revision output against channels, etc.