I think the idea of doing fasting to set your basal is wrong. Because…you are normally not fasting.
When someone does that, they are finding the perfect basal rates for a fasting state. Great. That will work well when they are fasting. And then will confuse them when they are not fasting.
A fasting state is not like a fed state. It would be like learning to fly in only a simulator and never actually getting in a plane. It just isn’t the same thing.
I know the general belief in D Land and by the endos in D Land is that basal has nothing to do with eating. And people who write books about it tell you to do fasting basal tests.
But they are just plain wrong. Or in reference to my flight simulator analogy, they are plane wrong.
Your basal rates have a lot to do with how much you are eating. You cannot separate basal from food consumption.
I am glad you are making this connection. Here is a post about it that is somewhat similar to what you are finding.