Possibly the best show on cable television. Makes me wish i'd gotten in on this discussion earlier. The reason I definitely think the flashback worked in this episode, as Brando pointed out, BB doesn't play its audience for a fool. But even more so, the obvious reason for it working is that hank is actually putting it together in his head. This is also why I believe they had good reasons to use a more dramatic take of Hank's delivery of, "Walter White?"
No one needed to see it, but Hank has to know he was on the right track the whole time. Which could be one explanation the new delivery of the line, aside from adding to the drama. Really awesome.