You need to see it IN MOTION - that's the point.

We're not saying there is grain there where there shouldn't be, or vice versa.

What we're saying is that real film grain CHANGES from frame to frame, while the grain on the window-frames stays static and EXACTLY THE SAME throughout the entire shot. That's not what grain is supposed to do.

Watch the 720p ion cannon clip, which is where this comes from. If you look very closely at the officers' uniforms, you can see very faint grain that MOVES as the clip plays. But if you look at the gray window-frame behind the officers, the grain does NOT MOVE at all as the clip plays, which makes it look unnatural.

I also noticed while looking at the clip again that the grain on Hoth is static, as well, but it's not as noticeable because the planet is moving slowly.