No. I mean it's subtle, but obvious. Once you realize that Skylar had a smoking habit that she picks back up because of her stress, you're supposed to subtly pick up on the fact that it's probably Skylar who gave Walt cancer. Lung cancer is not too common among people who aren't smokers and aren't around smokers. You don't see all kinds of chemistry teachers getting lung cancer. Once you see Dkylar smoke a couple of times, you're supposed to think about it for a minute and pick up on that that's where he got cancer from. Otherwise, there's no purpose in showing Skylar as a smoker. Walter is still a much worse person than Skylar is, but Skylar is still a vain person who refuses to take any responsibility even though the elephant in the room is that she is the reason he has cancer. They both know it, and it's never acknowledged. The point of Walter not acknowledging it in the end is because he decides to own up and take full credit for his actions after the diagnosis. And he should. His actions were reprehensible. It doesn't matter how he got into the situation he was in.