[Dovecot] is it necessary lmtp and director to avoid index corruption in mail delivery?

Hello all, If I have several postfix/dovecot-lda boxes with shared nfs storage, how director helps in this scenario? is it necesary to use lmtp instead of dovecot-lda?

With postfix/dovecot-lda boxes incoming mail happens at the smtp layer but director redirects are working in the lmtp/imap/pop3 layer.