debci-setup logs don't clean up as intended

debci-setup has code to have the logs owned by debci:debci and deleted after 20 days:

log="$debci_log_dir/debci-setup.$(date +%d).log"
touch "$log"
user_group=$(stat -c %U:%G "${debci_log_dir}")
chown $user_group "$log"
ln -sf "$(basename "$log")" "$debci_log_dir/debci-setup.log"
chown $user_group "$debci_log_dir/debci-setup.log"
find "$debci_log_dir" -mtime +20 -and -name '*.log' -delete

however, what I'm seeing on the ci.d.n hosts is that all the files are owned by root:root, log files older than 21 days are present and log files have historical data older than a month.