Maybe they prompted "make it sound like the guitars have D'addario strings"

AFAIK, a lot of commercials, particularly for cars, haven’t really shot the physical product in decades and instead used CGI. I think Ikea also makes heavy use of renderings. It’s all kind of insane. OTOH, a hundred years ago ads all used illustrations… I guess you’d have to show that the real strings don’t sound or behave as shown in the video, however it was created.