Reading through the man page for at(1), it mentions of the atrun cron job: "If a finer granularity is needed, the system crontab at /etc/crontab needs to be changed." However, atrun is no longer run by the system crontab in "/etc/crontab", but rather in "/etc/cron.d/at". The man page should be update to reflect the new path.
A commit references this bug: Author: allanjude Date: Fri Jul 17 20:43:00 UTC 2020 New revision: 363286 URL: https://svnweb.freebsd.org/changeset/base/363286 Log: at(1): Fix location of at(1) crontab With r318443, atrun was moved from /etc/crontab to /etc/cron.d/at, but the man-page was unfortunately not updated to reflect this. PR: 248048 Submitted by: debdrup Reported by: yoitsmeremember+fbsd at gmail.com Reviewed by: Pau Amma <pauamma at gundo.com> Sponsored by: Klara Inc. Differential Revision: https://reviews.freebsd.org/D25709 Changes: head/usr.bin/at/at.man
Thank you for the report.