Georgi posted a study showing that only 4% of people who are "pre diabetic" ever become "diabetic." It's a scam.
No study needed really is needed.
The metric HbA1c is downright useless and misleading.
When it comes to the stability of blood sugar over time, which really involves having more than just one data point, the oversimplication in the use of one data point, much less one that doesn't represent or serve as a useful proxy for blood sugar, only leads to people being guided by blind men donning white lab gowns to the lemming cliff.