This shouldn't be a surprise. They promised by the end of the year which they're legally bound to, at least to some degree, and this gives them a month of disaster recovery to delay it if something goes drastically wrong but that likely won't happen. And it's just like the last few expansions timing wise and literally every expansion at this point in beta has had people screaming "It's not ready and can't possibly be ready by then!" and yet every time they released it anyway lol.