Over in https://bugs.debian.org/860745 , Enrico suggests improved wording for when the daemons are older than the current /usr/bin/gpg:
gpg: WARNING: server 'dirmngr' is older than us (2.1.17 < 2.1.18). Run with --verbose for details. gpg: further info: Outdated servers may lack important security fixes. gpg: further info: A restart can be forced using "gpgconf --kill all"