There is one correct answer. The way the question is specifically posed, the contractors are wrong. If the bulb sensitivity was reduced, it would actually take MORE heat to actuate, resulting in a HIGHER activation temperature. Therefore the account is a myth.

Someone with expertise in the specification, design, performance, and testing of sprinklers would be better able to explain how concepts such as properties of materials, differential temperatures, heat transfer, etc. apply here. This is why it's important to understand things like thermodynamics.

Allan Magee, PE