The AuthPF shell is a pseudo-shell. The authenticating user does not get anything other than a text message on their ssh terminal session, and keyboard entry is ignored. The
shells(5) configuration file need not be altered, since that is to restrict end users to a list of authorized shells when they change shells on their own.
If you have a shell user who will -also- need authentication via AuthPF, that user will need two accounts.
Please see the
AuthPF chapter of the PF Users Guide.