The 2011 Blu-ray grain is mostly fake grain, so it doesn’t really represent the films as they would normally appear. Nevertheless, the negatives would still have quite a bit of natural film grain – less than the 4Kxx projects, but maybe only slightly less than 4K83. The real odd-looking ones are the UHD’s. The only significant grain to be found on them is frozen grain.
I’ve heard of Blu-ray releases “de-graining” old films, but I’ve never heard of adding fake grain. Why would they do that?
It’s pretty common. They degrain the film first, so that they can do major image enhancements without the grain causing weird effects (i.e. so you can boost the yellows or the sharpness without having yellow/extra sharp grain, also for 3D conversion so you don’t end up with 3D floating grain). Then, because the image looks like crap without grain, they add it back in at the end, after all the image adjustments have been made. People blame Lowry for inventing the degrain/regrain process, and I’m not sure where it really started, but it’s widespread. Some places go through more effort than others to make the added grain look natural and filmstock-accurate. Rarely does the film end up looking as grainy as a film (negative) from that period really would, so the whole process is still a net loss of grain (so a “de-grained” Blu-ray likely still has added fake grain). In these cases, the grain that’s there isn’t from the film, it’s from a computer. “Filmic” is what reviewers tend to call it when it works well.
What the UHD versions of Star Wars are is the version prepped for 3D conversion (so scrubbed as completely as possible of grain), but the 3D project was abandoned. Normally such a film would be fake-grained back up before a 2D release, but apparently nobody got the memo.
Ideally you wouldn’t bother degraining and regraining, but film negatives often have wildly differing colors than the original projection prints, so if you have a process that starts with scanning negatives (and people tend to like seeing all that extra fine detail on their Blu-rays that comes from the negatives), color grading and grain management usually just have to come with the package deal. But as with everything, there’s how to do it right, and how to do it cheap, and you can get wildly different results.
For an example of what they’re trying to avoid through degraining, mess with the sharpness setting on your set. Go ahead and turn it up to 11, then watch a grainy movie. It’s… not right. Also keep in mind that most displays are sold with default sharpness settings that are not zero, so grain really does genuinely look wrong for most people, because their sets are pre-configured to make grain look bad. The correct setting for sharpness on your display is always zero.