I thought that was standard due to the fact that banks will not approve financing above the appraisal value, so a buyer is responsible for making up the difference in cash if the appraisal does not match the asking price. A buyer CAN choose to make up the difference, but I thought that clause was pretty standard due to financing issues. But maybe it's regional? We had no contingencies, but we still had that clause in our contract.
ETA: ours was a multiple offer situation, so we offered above asking price and we truly were not sure if the appraisal would match.