A narrower edit than it looks
Replacing a sky sounds like the easiest thing on this list, and it is the one where models most often overreach. Given a new sky, a model will happily warm the render to match it, lift the shadows, and quietly tidy the power lines out of the frame while it is there.
All three are defects. The first two make the composite obvious; the third changes what is being sold. So the instruction is explicit that the light on the building does not change, and every render is compared against the original before you see it.
What stays
Anything silhouetted against the sky is part of the property's context: wires, aerials, branches, the neighbour's roofline. A listing photo with the cables edited out is a photo of a house that does not exist, and several rulebooks name utility lines specifically.