Just to clear up a point, digital images don't have "grain" they have "noise". "Grain" is the random physical texture made from small metallic silver particles found on processed photographic celluloid. "Noise" in digital is random variation of brightness or color information in the images captured as the result of degradation in image signal caused by external sources. Now you can simulate "grain" to some extent via software, but it's still "noise".
Whether "noise" is objectionable in a large print is a function of cropping, file resolution, PPI, and viewing distance of the print. In a 51.4 MP GFX medium format image unless its cropped heavily (which it doesnt appear to be) there is more than enough data in the file to provide sufficient resolution to print up to 16x20 or even 30x40, without objectionable distortion caused by noise in this particular image. Obviously you will not be viewing a 30x40 at arm's length from your face, like a monitor.
Finally faux grain and selective color as used here were composition choices made by the photographer. As viewers we all have the choice to like or dislike his composition, but beyond that, the fact remains that it was his choice, and as the viewer should be respectful of it.