Likely it has to do with the scaling of the actual property being measured. For example with decreasing temperature, steels become less and less able to resist

Likely it has to do with the scaling of the actual property being measured. For example with decreasing temperature, steels become less and less able to resist impact damage. Thus getting hit by something small at cryogenic temperatures is equivalent to being hit by something big at normal temperatures; so if you want to test whether a submarine can survive an impact that would be impractical to simulate in a lab, you could instead cool your test sample down a lot and test it with a smaller, cheaper device. My knowledge of shipbuilding is limited but I believe the navy suffered quite a bit during WW2 from certain steels undergoing a transition in the low temperatures of the north atlantic that caused brittle fracture. I would imagine testing at ultra low temperatures accelerates the rate at which such brittle fractures can be detected.