By "encrypted filenames" what people are clearly talking about is making it so unauthorized people can not infer from the filename of a password file what website that password is for.

For instance, to store the password for www.example.com, the filename could be derived by encrypting the website name (www.example.com) with AES using the user's master password, base 64 encoding the output, and using that for the filename.

Have you seen encFS?

Filenames readable in cleartext is a security issue. This means whoever has access to your files knows you have accounts on certain websites they are looking for.