This shows the huge variability. The AUC = area under the curve, which means they give you food, then you have a response that is measured on the continuous glucose monitor. They look at data for a certain time period, say 2 hours, after you eat. Then they see what your blood sugar level is every so often. They try to determine how much area is under that. So, people who are high for a long time would have a higher AUC than are people who are high but for a shorter time. And it looks like there are people who don’t have any response (the dots near zero):

This where the point about insulin is relevant. Some of the folks who have low AUCs have them because they way overproduce insulin. If these folks where given Kraft tests (take a sugar drink, measure both insulin and blood sugar), you’d see a huge insulin spike. That’s why blood sugar doesn’t go up much.
Could there be folks who don’t get high blood sugar (very low AUC) and don’t have high insulin? I don’t know.
Edit. I drew this up to show the area under the curve. The purple has the highest AUC, the red has lower AUC, and the people near zero are in black:
