IANA nutritionist or expert at all in this area so take this with a grain of salt, but my understanding from looking into it is that the sugar alcohol doesn't break down in digestion and isn't absorbed, that's why the "carbs" from sugar alcohol "don't count."
I would recommend taking it easy on the sugar alcohols even though they "don't count" because they can cause significant gas ;-)
And some like xylitol are highly toxic to dogs, must be careful around them.
It depends on the type. Some are partially digested as carbohydrates. Others are not. You can look up their individual Glycemin Index.
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