Honestly?... I think those recipes have been made up by people who don't question what they see.

I have taken several recipes that call for these 'multi' starches and made them as the recipe called for and then with only arrowroot... guess what... they turn out exactly the same.

The thing is... a lot of people who make up recipes don't always involve themselves with the 'nutrient value' of the food. They are more taken with the final product and the cost.... maybe a caloric count.

Another thought is that... Maybe they are trying to get the benefit of the arrowroot (if they know about it) but cut down on price by 'cutting' the arrowroot with cheaper starches?