It is possible that they waited to decide who the Mule would be until later on (either to be topical, to avoid leeks, to make it impossible to accurately guess, or just because they wanted not to be able to telegraph it). In that case, contradicting information would be natural and is just ignored.
I suspect that they didn't want it to be Magnifico because 1) no surprise to those who read the book (and moreso than, say, GoT, I think they think a big part of their audience will have done so), and 2) the original reveal has the rather squicky 'Magnifico implies he would have mind-controlled Bayta into being his love-slave to get an heir, but alas, he is a mule in all too many ways' stinger that would have hit like a freight train nowadays. For that reason, I don't think it's a double-fakeout and he's really still the Mule.
What's really surprising about it being Bayta is that she was really the audience surrogate in the book, and so for those of us who read the books, it's making your favorite character the villain.