I think he said it was siding, in which case, it would keep its own color for more than a year without any finish. You're right though about roofs.I don't see how you would allow yourself to be held responsible for shingles that faded, especially a 45K roofing job. You put exclusions in the contract stating such. If they were decorative shingles then a semi-solid or solid stain should have been used imo. I would never stain shingles on a roof, just let them turn gray.