https://www.bariatricpal.com/magazine/556-fact-or-myth-the-5-day-pouch-test/
Yes, it's fundamentally a fad diet. The basic premise is that since most were on a liquid diet just after surgery and we lost weight like gangbusters then, all we have to do is go back to a liquid diet again.
Reality check - even those of us who were never on a liquid diet still lost like gangbusters initially, as that initial drop has nothing to do with the composition of the diet, only the very low calorie level that is forced upon us by the recent surgery.
If you want to do a "reset", go back to a basic meat and green vegetable diet to help you detox from whatever junk has crept back into your diet.