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There is another possible explanation that has been overlooked as to why Porsche chose a 180 T-stat for their cars ... creature comfort.

Germany and most of Europe has long cold winters and a car with a 180 T-stat has a cabin heater that ROCKS. That extra 20F makes a big difference in keeping the cabin toasty on a cold winter evening. I believe many German cars; Porsche, VW, Audi, BMW, MBZ choose a higher Tstat for this reason. One of the many compromises a car company must make when designing cars for the masses. Since a GT3 is primarily designed for motorsport and not winter driving I suspect the 160F T-stat made more sense here.

When choosing a T-stat for your car consider your typical usage. If you do a lot of winter driving the 180 might be the right one for you. If your interest is Summer driving and motorsport than a 160 would be a good choice.

I have no MBA, SAE, just a measly BA in business. I have no documentation or internal memos to support this theory. Just a basic understanding of cooling systems, an observation that most German cars have a higher T-stat, and that their cabin heaters are "the best" when it is cold outside.