The last sentence of the second paragraph under the Description heading of cron(8)says. "The cron utility also searches for /etc/crontab and files in /etc/cron.d and /usr/local/etc/cron.d which are in a different format (see crontab(5))." On review of crontab(5) there is no mention of a "different" format for those 2 paths, IE: /etc/cron.d and /usr/local/etc/cron.d I think the second paragraph needs to be rewritten to clarify to the reader exactly what the cron utility is expecting as a control file. The following is my draft of what it should say. The cron utility uses a file formatted as defined by crontab(5) to control it's actions. The host system default is /etc/crontab which should not be changed. Additional crontab(5) defined files with unique file names may be placed in /etc/cron.d or /usr/local/etc/cron.d also /var/cron/tabs may contain files named after accounts in the /etc/passwd file as documented in crontab(1). File content read from these path locations are merged together and loaded into memory for use by the cron utility.
After reading what I posted I see I was not very clear about what needed to be changed. Only the second paragraph under the Description heading of cron(8) needs to be replaced with the following paragraph content. The cron utility uses a file formatted as defined by crontab(5) to control it's actions. The host system default is /etc/crontab which should not be changed. Additional crontab(5) defined files with unique file names may be manually placed in the /etc/cron.d or /usr/local/etc/cron.d directories. Also the /var/cron/tabs directory may contain crontab(5) defined files named after accounts in the /etc/passwd file as documented in crontab(1). File content read from these directory locations are merged together and loaded into memory for use by the cron utility. Issuing the "service cron restart" command from the root host console will refresh the cron utility's in memory controls.