I think this statement is wrong. Though prediabetes is generally used to referred to patients who are prone to develop type 2 diabetes and may be able to reverse the trend through diet and behavior modification it is still possible to catch someone who will develop type 1 diabetes before they are full blown and making no insulin. It is a gradual process whereby the antibodies destroy the insulin producing cells of the pancreas and the blood sugar gradually rises as the pancreas can no longer produce enough insulin to control the blood sugar. Someone does not just go overnight from normal insulin production to making no insulin so it is certainly possible to catch someone in a phase where their HBA1c is gradually rising but they are not full blown type 1 diabetes.