This is not correct. When someone with type 1 has an illness they can develop ketones while their glucose appears stable within range. This is can lead to death. About once a year, when my son is sick, we need to monitor his ketones with finger pokes. When he has a stomach bug and can't eat, we have had to go to the hospital for a drip to allow us to give insulin and lower his ketone level. Having ketones on the CGM with glucose would have been very helpful.