I don’t think it was meant to be a “green means it’s good to deny it”
I think it’s more the general association that red means “Stop” or in this case “Don’t” and Green means you can
No, it’s intelligent.
Youtube would kill his videos if he just left them alone. Changing the thumbnail allows him to make revenue. It also probably makes people watch the video because they’re confused about the thumbnail and where in the video it’s from.
It’s smart as hell.