Not sure if this is the right forum for this as its just a general question...

I've seen several mentions to the effect that white potatoes are basically off limits forever while sweet potatoes can be eaten in moderation when one is on a maintenance phase of their program.

Both Sugar Busters and Atkins seem to mention this but I can find no reason to see why this is the case. Every carb counter I counsult shows the two to be similar. The one on this site indicates:

(Food item, 100 g portion.
Click on items for full details. Carbs per 100 g, Fiber per 100 g, Protein per 100 g, ECC per 100 g)

Sweetpotato, cooked, baked in skin, with salt 24.27 g 3.00 g 1.72 g 21.27 g

Potatoes, baked, flesh and skin, with salt 25.23 g 2.40 g 2.30 g 22.83 g

Why do sweet potatoes get a free pass?