I did this for drywallers... They either don't get the location right or just forget to take the cable out..plus trying to save some money for this client

Not all cameras can cover a black gang box. Even if you put a cover plate on and mount the camera, it looks tacky and unprofessional. This video is actually a pretty good idea! My only concern are the asshole drywallers that would screw with the Romex and completely remove it.

Yes even though its unlikely there would be any noticeable interference for a security camera, I like to go that extra mile just in case something comes out in the future that IS more sensitive to EMF.