I'm reading a book at the moment (the diabetes miracle - Diane Kress) in which she talks about how type 2s usually produce too much insulin, gradually straining their pancreas more and more. This is identifiable, even in pre-diabetics, as a lower BG level after eating than before. This often doesn't show up on a 2 hr post prandial test, but will show up if the testing continues or 3 or 4 hours. The pancreas has simply released a squidge too much insulin, which lowers BG, which stimulates appetite, which leads to eating again... And there you have it - the cause of carb cravings.
And she says it is usually only visible on longer term tests than the 2 hr ones.
You could test this theory:
Eat a meal with no carbs in it whatsoever (not even a green bean), and see if your test results are different from normal (no drop below starting level)
Of course that is assuming your meter is accurate enough to capture these variations.