Your attention to the glycemic index of rice versus potato is perhaps misplaced. Much longer times of digestion and hence satiety are achieved via proteins and fats.
Thus a diet high in fat and protein would take more time to digest than a diet based around rice or even potato.
The preponderance of meat and saturated fats and the protein and saturated fats of dairy products in a western diet of some generations past would have out-weighed the relatively low values of fat and protein in eastern cuisines.
But dietary habits have changed in the ‘West’ since then. Its no longer a status marker to eat meat and dairy. There are fusion cuisines that are carbohydrate-heavy and fat-light.
Of course, this is all IMHO. Please feel free to refute, rebut, and vigorously oppose my offering.
The OP may want to check out the technical paper which talks about the developed Satiety Index. Potatoes stood out far above any of the meats or fats in their study.
Holt, S.H.A. et al. “A satiety index of common foods” European Journal of Clinical Nutrition 49 (1995): 675-690.
I had the same thought, until I reread and saw that the study compared equal caloric quantities of the food. Three ounces of ground beef, cooked, has 250 calories. To get the same amount of calories, you’d need almost ten ounces of potato.
What would account for the difference, water content? Because I would expect a potato to be pretty much pure carbs, while beef would be mostly protein plus some fat, and gram-for-gram, carbs and protein have the same number of Calories, while fats have over twice as much (IIRC, 4 Calories per gram for carbs and protein, 9 Calories per gram for fat).