Filezilla encryption options

Greetings! Running Enterprise Edition 13.0.6.0 64 bit. Adding a session for FTP, with Filezilla as the underlying utility, and can't set/disable the encryption. In RDM, on the 'General' tab, with 'Application' set to to 'Filezilla', and protocol set to 'FTP', the box underneath that is greyed out (see attached). This causes a connection using SSL, which won't work with this provider. If I launch directly into Filezilla and open its site manager, and configure the same site, but set encryption to 'only use plain FTP (insecure)', I connect without issue. I don't see any other field in the session settings that seems relevant.

Thoughts?