I thought the same thing. This is clearly the biggest twist in the movie. Tho it is also still dead last on the list (even behind the one the included) because every single person with any knowledge of the comics whatsoever, predicted that Marion Cotillard was really Talia. Like from the first day she was cast. There wasn’t a single moment where I (& the vast majority of the people with knowledge of that character) didn’t think she was Talia.
It was an uncharacteristically obvious twist for Christopher Nolan, & it (plus the fact that Talia was the weakest villain in the trilogy by a wide margin) is a major reason why The Dark Knight Rises is the worst film in the trilogy (tho I’d still argue that it’s pretty good).