If you look closely, at around 0:22 it causes some artifacts in the rifle's red light matrix thingy. It could be regular compression artifacts, but they look like denoising artifacts to me.

Could it be just an intentional focus effect?

TIL, thanks. That's a more prosaic answer than I was expecting but clever and makes sense.

How "local" are such techniques? Is the DL network doing things like "this is a car, and this is a patch of it, so it must look smooth"? Or is it more like "this patch is noisy, so let's make it smooth and hope for the best"?

More on the local end. Traditional denoising is edge finding + blur; you find the edges that you want to keep crisp and you blur on both sides of the edges. ML has been really good at somehow replicating and improving upon that result without explicitly building any sort of understanding about what it is that it's denoising.