I'm not sure it's carbs... I mean, who knows? Maybe it is. But I don't usually crave carbs in the form of breads or so-called high-carb foods. It's more the horribly sweet sticky stuff (like dulce de lece) or caramel coffee drinks.
My plan-- such as it is-- is to do it for three days and then make a very sensible no highly-processed foods diet. For me that actually means not eating fake meat, either.
Why do it? Not at all because I think it's a panacea, etc. I don't. I think that for me it's more just the idea of-- well, literally, a reboot. I go for months and months doing really really well on how I eat. (lost 25 pounds since August... hella slow, but I'm old and am hypothyroid), but then I do seem to go on these binges. So for me this is just a way to pull myself together.