Is There Much Difference Between - 10c & - 40c On Freeze/Thaw Cycles?

No, not really.  When water freezes to ice, it occupies 9% more volume than that of water. Once it's frozen, that expansion is done. There is no further activity, even if the temperatures continue to plummet past cold winters.

Freeze/thaw is important in sculpting materials because it is an ongoing cycle of expansion and shrinking right around the freezing point, at +- 0C. Once the temperature is past frozen, it's more important/noticeable for us living beings.