I'm not sure I understand, as far as I can tell his use case is purely for symmetrical encryption of files? Then why not simply use openssl or something similar with their favourite cipher?

Why do you need to generate a private key from a passphrase instead of simply deriving an encryption key directly?

I actually do that from time to time when using GnuPG is not practical:

    openssl aes-256-cbc -a -salt -in <cleartext-file> -out <encrypted-file>

And in order to decrypt:

    openssl aes-256-cbc -d -a -in <encrypted-file> -out <cleartext-file>