I think you would have to have two consecutive nights of similar temps and follow a similar evening routine to be able to accurately determine.

I have wondered the same thing but have not had consistent enough conditions to test. Three weekends ago, I was out and it got down into the upper 20's F. I wore most of my clothes to bed that night (sleeping in my hammock with little wind). This past weekend, I was out and the temperatures were in the mid 30's and I wore just poly-pro long johns and socks(same sleep system).
Comparing the two nights, I did not get as cold wearing just the long johns, but we're talking at least a 10 degree difference in the temps.

So, I really don't know what is the answer.

Tango61
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