Because of beat patterns from the vertical deflection of the TV with the film cameras used in TV shows or movie production, they'd never use a TV that was presenting a picture when filming a scene. They'd paste in the desired action on the TV set screen later in "post -production". This in turn allowed movie and TV show makers to use "fake" TV sets (ones never actually manufactured) in their productions. Or place color action on a B&W set.
This TV in this thread is like such an animal.