I don’t see how a pressure washer and bleach can damage the color of vinyl siding.
It looks to me that light areas are the only ones that are clean.
Kwik, actually I am guessing but I think the areas that are clean are the dark areas. Usually with vinyl you get that whitish/almost chalky oxidation that can be difficult to remove. It looks like her friend set up a ladder and the ladder blocked the ability of the pw to do its' job. Or, he could have forgotten to get that area after moving the ladder. Just a guess tho.