The way I understand it is thus. When you eat carbs, you spike insulin. There’s no way around that at a certain level of carb intake, and this level varies some rather small degree from individual to individual. (“Small” could actually be a rather large percentage difference, as some might tolerate 75 grams of carbs a day, while others much less, but no one eating a SAD with hundreds of carbs a day is likely to not be producing insulin spikes.)
And it is the insulin that crushes ketone production. You either have insulin, or you have ketones, but you cannot have both to any serious degree. When insulin is high, ketones will be low, or not detectable, and they will not be being produced. I’m open to being set straight by anyone who can show me this understanding is incorrect.