Is there a test of originality for copyright? I wouldn’t call myself vehemently anti copyright but when the idea of “let’s just not play and the ambient sound of the orchestra sitting there is music instead” is the basis for the copyright it does make me question the validity of it. When someone who has done XYZ drug of choice and can come up with that idea in their drug addled state of mind as a pretty good first pass (if I were to to smoke marijuana and you asked me of a clever avant garde music idea, the concept of 4’33’’ is probably be one of the top three I would just list right off the bat not knowing of Cage) I really do question whether you should be able to copyright that idea. It’s even a bit of a hippie meme “what if the music is everything around us? Har har”
By the way I love 4’33” and don’t denigrate it - the way Cage executed the idea is flawless - which is one of the reasons it’s so timeless. I just don’t think it’s something you can copyright. And indeed, the stories you linked indicate that, though rather than point out the ridiculousness of the situation they simply used it as a money and publicity making opportunity.