When to use "pkill..." flag in newsyslog.conf?

I'm configuring relayd to log to its own log, and I'm not clear on whether I should run "pkill...". I can see the following in the default newsyslog.conf:

# logfile_name		owner:group     mode count size when  flags
/var/log/maillog			        640  7     *    24    Z
/var/log/pflog				        600  3     250  *     ZB "pkill -HUP -u root -U root -t - -x pflogd"
/var/www/logs/access.log		    644  4     *    $W0   Z "pkill -USR1 -u root -U root -x httpd"
/var/www/logs/error.log			    644  7     250  *     Z "pkill -USR1 -u root -U root -x httpd"

I included the maillog line to show that there is no "pkill..." flags command for a log that is for a single daemon, which at least seems similar to my log configuration for relayd.