Commit https://cgit.freebsd.org/ports/commit/ports-mgmt/pkg/pkg-plist?id=3e8236085199a7aa24fe60fadf8a9777612b54d2 added etc/periodic/security/405.pkg-base-audit. This file is also provided by security/base-audit.
Here's a sample from Synth building my local metaport first pulling in ports-mgmt/pkg and later security/base-audit.
===> Installing existing package /packages/All/base-audit-0.5.pkg
pkg-static: base-audit-0.5 conflicts with pkg-1.18.1 (installs files into the same place). Problematic file: /usr/local/etc/periodic/security/405.pkg-base-audit
Failed to install the following 1 package(s): /packages/All/base-audit-0.5.pkg
security/base-audit will be removed as it is no longer needed.
I said it almost a year ago when merging to pkg was started but it was not done and nobody updated / closed original PR 212306