If you look up how to calculate the glycemic index of a meal, the formula treats each meal component's glycemic index as a proportion of the total meal's glycemic index.

But the above example shows that the body doesn't treat food in that manner - the relatively low carb, higher fat cheese didn't smooth out the higher proportion carb count of the toast.

In the paper, the largest carbs for the ultraprocessed meal was instant mashed potatoes, while the non-processed meal had bananas as the largest carb source followed by craisins/cranberries.

The high carb foods in the unprocessed meal are paired with fiber.

The high carb foods in the ultraprocessed meal are NOT paired with fiber.

The fiber slows the rate of carb intake.

Same thing occurs with protein - same amount of ground beef and steak, ground beef meal will result in faster amino acid ingestion than the steak meal. No idea if there are any pros/cons of the faster ground beef ingestion, but there is a difference in how the digestive system processes the two meals.