An organization using SAN records in their certificates wants to ensure all hostnames are properly...

Modern browsers and operating systems (such as iOS and newer versions of Windows/Android) often ignore the Common Name (CN) if Subject Alternative Name (SAN) fields are present. If an administrator puts the primary hostname in the CN but forgets to repeat it in the SAN list, the client device may reject the certificate as "Invalid". Best practice is to include every possible FQDN and hostname the server might be accessed by within the SAN section.