The implication of it all being Cobb’s dream is that Mal woke up when she “killed” herself — that’s a common technique they used for waking — and Cobb is still asleep. At most, he made it to that level he thought was real and Mal thought was a dream.

One of them has to be wrong. The surface assumption is that Mal is wrong, because that’s what Cobb thinks. But, as I argued, the rules of dreams say Cobb is wrong. And the implications of that are pretty messed up.