Agreed. The brains of keto-adapted individuals can use ketones as a source of energy which are much more stable, although for a long time it was believed that brain relied on glucose.
My layman understanding is that glucose is the first choice. But stay off it for a day or two and the body starts turing fat into ketones as an alternative.
Yes that accords with my layman understanding as well. The body will go down the "path of least resistance" for energy and glucose is easier to metabolize than ketones. Deprived of glucones, the body will switch over and hum along once adapted.