Yes, I’ve run into the same thing. I’ve come to learn that when a product is labeled “Sugar Free”, it does not always mean it has a low glycemic index (GI).
An example includes Sugar Free Jello. The Jell-O brand contains Maltodextrin, but I’ve found Walmart’s generic brand (Great Value), although also labeled “Sugar Free” does not contain Maltodextrin (it contains Aspartame as a sweetener).
I found it interesting that Dr. Westman’s Heal-Clinics has a recipe for for Sugar-Free Chocolate Mousse. The recipe calls out for 1 box of sugar free pudding mix. The only sugar free pudding mix I can find is produced by Jell-O, which contains Maltodextrin. Only thing I image is that the quantity of pudding recommended by the Heal-Clinic is so small that it has a small impact on the overall GI.
Lesson learned is that although a product is labeled “Sugar Free”, it does not always have a low GI and comparable products may have different ingredients that are acceptable.