They have one picture where they like the left side of the dock, but say that the AI screwed up the right side. And they have a previous one where the right side is good but the left side is bad. And they are frustrated that the AI can’t or won’t make a single generation where both things are good.
And the two pictures have the same structure, same illumination and look barely distinguishable otherwise. That is the case where editing is trivial.
You might wonder, how often does this really happen in real life, and the answer is: all the time. You get a picture you like overall, and it looks good from 10 feet distance but on closer inspection you notice some blemishes with it. One way to fix this is to “inpaint” the blemishes. Basically you tell the model to keep all the pixels unchanged, but generate new ones in a small region masking out the blemishes. And of course you run many such inpainting generations and pick the best. And when you have multiple blemishes, which is often the case, then very often one gets filled in good in one generation while the other is better in an other. And you can keep rolling the dice hoping that some day the AI will get it right everywhere, or you can get them in photoshop and do the selection manually.