You are correct. Normal people should eat low glycemic foods also, true. But, not for the same reason that diabetic people have to. A diabetic person can't handle spikes in blood sugar, while a normal person can without consequence.
What is interesting is the mechanism that causes low glycemic food to digest slower. It's the fiber! Processed Uncle Ben's has .6 grams of dietary fiber per serving while brown rice has 3.5 grams per serving. For the same reason brown rice takes much, much longer to cook breaking down the cellulose to make it palatable, brown rice takes much, much longer to have it's energy absorbed into the blood stream, the fiber.
When a person eats low glycemic therefore high fiber foods, they are getting the same amount of satiation per same quantity of food, but that fiber is passing through without being absorbed. So, people eating low glycemic foods are consuming less calories for the same level of satiation. That is the 10,000 ft view but it more complicated than that because different foods have different levels of satiation based on many things that are more than just physiological but also psychological.
The article says that high blood sugar levels lead to weight gain which isn't entirely true in most people. High blood sugar levels while the liver has stored as much energy as it can in the sugar analogue glycogen leads weight gain and eating low or high glycemic foods doesn't matter.