Very low carb does lead to insulin resistance in many people. When glucose intake is low, much of the body's cells convert to fat burning and become more insulin resistant and less ready to take on glucose. THis preserves available glucose for those few cells that require glucose for fuel. This is a natural process and is not the same thing is diabetes/hyperglycemia for several reasons. The first is that it is quickly reversable within a few days by increasing carb intake. Your glucose processing system is still fully adaptable to various conditions the same as any healthy person. It's just that when glucose intake is low, it naturally adapts, but if glucose intake were to rise again, it quickly adapts again.
The other issue is that with true diabetes, your blood glucose is out of control and gets dangerously high. That does not happen with the insulin resistance brought about by very low carb eating because you are not eating large amounts of carbs and your body is adapted to the carb you do eat. So your blood glucose should remain stable and not spike after eating. The exception would be if you surprised the heck out of your body by suddenly pounding down a load of sugar all at once. Because your body had adapted to very low carb, the sudden sugar intake would catch the body flat footed and it would take a few days to fully readapt to higher carb intake.
However, for some few poeple, it does seem that very low carb results in kind of high resting blood glucose numbers, but still, there should be no post meal spikes so peak blood glucose should never pass the normal range. I guess in some people, theoretically this could lead to slightly higher overall blood sugar levels, but only assuming that the person had higher fasting blood glucose but post meal glucose was not lower than previously. However, this would still not be a pathological condition like in true diabetes and the overall blood glucose scores would still be in the healthful.
Fasting blood glucose and response to a sudden glucose load is only part of the condition. THey use those markers as potential warning signs for a person that may have seriously too high blood glucose on a day to day basis. But those with adaptive insulin resistance would not have too high blood glucose on a day to day basis, just maybe slightly higher resting blood glucose. And their blood sugar control mechanisms would still be fully functional according to prevailing conditions.
With very low carb diets, insulin resistance is merely an adaptive mechanism to preserve glucose, whereas with diabetes, it is a breakdown of the system due to overload of glucose. It's like if a truck were sitting idle in the driveway, is it sitting there doing nothing because it has no load to carry and all the work is done, or is it sitting there because the truck is broken and so the load cannot be delivered? The symptom is the same in both situations and so to really understand the true situation, you have to look at the larger picture.