Think of it this way... you have two dimensions to the noise reduction filter... the "more often/less often" dimension and the "stronger/weaker" dimension.
The first time around, to avoid the smearing, I used a more often and weaker noise filter. This resulted in less overall video noise and because it was on the weaker side, the smearing wasn't completely intolerable (though you noticed it and I knew about the side effect all along). Of course my goal was to minimize the smearing while maintaing lower overall noise.
I realized that there is no way to really eliminate the noise without trading it off for smearing in the moving scenes or loss of detail everywhere, so on the new set I used noise reduction that is actually stronger (because it searches more frames at a time to decide what the noise free version is) but it is applied in full strength less often. What this means is that in the most still scenes, you get near perfect noise reduction, but as soon as you get any movement the entire frame basically reverts to the sharp, but noisy image. What it really means is that you don't get anywhere near as much smearing because no real noise reduction is being applied to the moving scene, PLUS since its moving you're less likely to be able to focus on any noise ANYWAY. This goes back to the whole reason some still frames may not look that great... if you freeze frame something that isn't perfectly still, you'll see the noise and it won't look that pretty, but in motion your eyes won't be able to follow it anyway.
Mind you, I didn't manually do this on a scene by scene basis, just decided on an overall setting once and used it for all 3 movies. When I say its "applied less often" it means that the algorithm that decides whether to apply noise reduction or not to any individual portion of a frame kicks in less frequently.