For one thing: kidney stone are a very common issue when ketosis is sustained for a long period.
That means that you always have ketonic bodies in your blood (checkable with a quick urine self-test), which may not be the case for many diets that are just low-carb and not strictly "keto".
They aren't? Are there strong hints* that this is true? I didn't see any so far, but that may be due to my limited research.