Perhaps you aren't aware, but even currently a substantial number of Type 2 Diabetics are not aware of symptoms before being diagnosed.
Now some of those will have had vague symptoms, but many have no symptoms at all!- I had none and I've still never had any since I found this forum very quickly!
On the other hand people like
@KennyA got symptoms when barely in the pre-diabetic range (which must have been really frustrating).
Diabetes is tricky and there is no completely satisfactory way of diagnosing all at risk (and only ones at risk) of symptoms/complications!