Absolutely not.
Everything in your stomach gets mixed up into one mass, so mixing GI's is DEFINITELY a way to slip some desert into your diet. If you had a big *ss salad, with chick peas, and some grilled chicken, and generally, 75% if your meal has a GI of 35, squeezing in a bowl of ice cream will modify the GI of your entire meal, and because you ate a low carb-high fiber meal, it'll digest slower, not spike your BG levels.
Throw in that ice cream and let your meal grow to a GI of 60, rather than waiting for your stomach to empty then throwing in a big bowl of carbs, with a GI of 85, and giving yourself a second spike.
Not suggesting people eat a handfull of peanuts to compensate for eating unnecessary calories, but if you're gonna do it, mixing a low GI food with a high GI one is DEFINITELY an approved way to to it without ruining your night.
