It is the sustainability of such rapid weight loss approaches that concerns me. After the initial 'reversal' a pwT2 would surely have to continue on a lower carb regime so as to maintain A1c etc.
Yes I wouldn't be at all surprised if LCHF became a very good approach to help maintain the weight loss, and unless the T2 was caught very early, also important to maintain good blood sugars. Some seem to have reversed it so decisively that they can get away with carbs so long as they don't regain weight however. But I'd question whether it's sensible to go back to eating "normal" levels of carbs.
Re speed of weight loss, I have to say, in all the reading around I've done, I don't think there is much evidence for the idea that rapid weight loss is particularly bad at screwing up one's metabolism. I may have missed a study which contradicts that of course.
All the meta studies I've seen so far suggest that the speed of weight loss makes little difference. Basically, if you've spent many years being obese then manage to get thin, then no matter how you achieved that, your resting metabolism is probably going to be reduced by around 15%. Potentially more.
Sustained weight loss seems to be just damned hard. People are going to be fat or thin. If people are predisposed to being fat, get fat, then work damned hard to get thin, they will almost certainly be spending the rest of their lives having to eat, say, 500 calories a day less than someone of the same gender, age and weight who was never overweight.
Add to that the fact that most people get T2 when they get older, so their bodies are already more inclined to gain weight and lose muscle. The battle is immense.
Interestingly, one of the most extreme weight loss regimes ever studied - The Biggest Loser - shows that, sure enough, 6 years after contestants broke their backs to get incredible results in a very short time, they had regained almost all the weight, and had reduced resting metabolisms. But - and this is the interesting bit - the people conducting the study also said that they had, in fact, fared slightly better than people who lost weight in other studies involving less rapid methods.
Anyway the beauty of LCHF, I think, is that it may help some people to lose weight, and while doing so will also help T2s avoid toxic blood sugars, and even if insufficient weight is lost to help reverse T2, or no amount of weight loss would reverse it for them, then so long as they stick to LCHF, it doesn't really matter.