I think that statistic is for people who allow themselves to get morbidly obese before they realize they should lose weight. Imo, people who get morbidly obese before they realize there's a problem are already a smaller subset of the population who have some sort of psychological issue to begin with, like food addiction, or it's a form of depression-related self harm that they later rationalize. Misrepresenting statistics like that is super helpful to keep other crabs in the bucket. The other part of weight loss failure statistics is that rational people usually don't let themselves get fat enough to count in the statistics, which usually start at "morbidly obese" or "obese".