I think they are trying to shield themselves from future expense. Walking away is a risk mitigation strategy. If they break a bunch of tiles they may not be able to get enough of the tiles to match the expiring ones. Customers get upset when they look like our roof did. With 3 or 4 different shades and textures of brown tiles after a decade. All because the original maker was out of business.That's possibly a great consideration BEFORE they already spent money and resources on design, 2 permits, and 6 man x 2 truck load and roll. By declining the job now, they're trading a possible profit reduction for a guaranteed financial and reputation loss.