Didn't watch that whole video but link points to specific spot in the video talking about SAN.. It only showed IPs not any dns, so its actually good practice to set your common name as a san as well if using them. It is possible from my understanding that some browsers depending how their makers interpret the rfc that is SAN is used to not use the common name.
So if going to create a SAN, you should do san with your IPs you will be using along with your common name, etc..
For example here is my cert on pfsense. See it has 2 fqdn dns entries and 2 IPs so I can hit pfsense via one of its other interfaces if I wanted too, that was more of a test example for another thread more than actual need. And it also has a common name set as just the pfsense.local.lan.
If you do want to hit your pfsense via some other fqdn you will have to adjust pfsense to allow that or you will get a rebinding error, etc. That would be in System / Advanced / Admin / Alternate Hostnames
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