Well, it fits with the present dogma so you can see why it's supported. And there's money to be made out of the soups and shakes, etc.
I do think it's possible for this approach to be useful for some people, and if it works for them, fine. I'd argue that an 800 calorie daily intake is going by definition to be a low - or at least reduced - carb intake. Even if the diet was 100% carb (and it isn't), then that's 200g carb maximum, which is probably going to be a reduction for many people.
The story does not make it entirely clear that after five years 23%, of 36%, of 298 subjects, were still in remission. I'm no mathematician but that looks to me like 24 or 25 people of the original 298 - less than 10% of the original group.
I had diabetic symptoms well before weight gain, and had lost no significant weight in the four months it took (on 20g carb/day) to get my BG back to normal. To my mind weight gain and loss is a consequence, rather than a cause.