No, Other Ira at 2013-06-18 16:18:49:
Scott wrote: "Nonetheless, we have a takeaway: We’re not Lehman and we don’t have the power and sway of Hitchcock behind us, so we must write set-ups that are locked down air tight."
I'm not sure about this, but I think it may be true: If you're not sure if you've locked down your setup air-tight, then (also) have your "world" committed to that setup.
And so in North by Northwest, first - This perhaps-not-air-tight element happens at the very start, and there are lots of other things happening; lots of energy.
Second - From very early on, the "world" in North by Northwest is revolving around the notion that Cary Grant IS Kaplan, while he keeps insisting that he isn't. And perhaps part of the reason the audience is willing to buy in is that, with all the things that do happen at the start of the film, maybe they think (at some level), "I guess I missed how that happened." Or, they simply don't care (so much, or at all).
It's akin to walking into a room and seeing a guy you met once, a few days ago, named Steve. But as you approach him, everyone is calling him Rick. You think, "Oh, okay." You say, "Hey, Rick." "No. It's Steve."
And so, maybe the film should have worked a bit harder, added another 1/2 page worth of action and/or dialogue to make that setup air-tight.
Or, it could just do what it actually did: Offer A basis for the mistaken identity, and then move on - with characters expressing 100% commitment to your setup.