passwd driver is used regardless of services.dovecot2.enablePAM value

This is enabled unconditionally in the extraConfig string here: https://gitlab.com/simple-nixos-mailserver/nixos-mailserver/-/blob/9f6635a0351c190179dc6904545f950108a23dd8/mail-server/dovecot.nix#L302. Originally, services.dovecot2.enablePAM disabled both pam and passwd drivers. What is the way to disable it?