My best guess is that it was a proof designed to verify the success of the casting process, not resistance to theoretical real-world exposure. All metals have

My best guess is that it was a proof designed to verify the success of the casting process, not resistance to theoretical real-world exposure. All metals have a ductile-to-brittle transition temperature. Ductile failures are generally preferred to brittle (think bend/dent vs shatter). Some steels have a D2B temp around 0°C, which makes them basically untrustworthy in colder environments. The D2B Temp can be lowered by altering the elemental makeup of the metal, controlling the crystal structure, and other various metallurgical techniques. These same techniques are utilized to produce metals with other desirable properties, like increased ductility, higher tensile strength, corrosion resistance, etc. Casting, especially large complex castings of custom tailored alloys, are temperamental. Controlling the elemental makeup is relatively easy, but controlling the crystal structure is difficult. My guess is that they were paying for a specific alloy & temper of metal because it had their desired properties, and successfully cast samples would have a D2B below -70°C. It is a standard & easy test to perform, but I could see how the tech running it would not connect the dots above. That being said, they don't need to know why the test was ordered & paid for, they just need to run it.