I don’t remember that anyone’s said Mandalorian’s “first episode spoiler” directly referenced The Rise Of Skywalker, just that it was a revelation that changed the way the saga is thought of. The phrasing in that article was weird in the first place, in that if it’s IN the show it’s not really a “spoiler” for anything, but frequently the meaning of words in entertainment writing are rendered meaningless. Try reading an article in the Hollywood Reporter where someone doesn’t misrepresent a direct sequel as a “reboot,” for example.