Your mind and health are impacted by your physical body. If eating a certain way impacts your physical performance then it might also have effects on your health (and mind) in unexpected ways.

I'm not saying that ketosis has this kind of an effect, but rather that eating or not eating some other things might. Eg vitamin K2. The body is be able to make vitamin K2, but we might have stronger bones and teeth, and a healthier cardiovascular system, if we get extra K2 from an external source.