Right, I see what you are saying. Your BMR decreases not directly due to fasting but due to the fact that you are a lower weight. The results of fasting (weight loss) leads to lower BMR. Whereas caloric restriction shifts BMR down regardless of whether weight is lost.

I agree with your anecdotal evidence. I do 36 hour fasts 2x per week, and otherwise do 20-22 hour fasts. Every now and then I do a longer, 48-72 hour fast. I am in awe of people that get to 5-10 day fasts and hope to work up to this over time, perhaps on a quarterly basis.