I think they are along the lines of "active recovery". Even some full body cardio-ish work is probably gonna work as well.
You use some extra w/o's with lighter reps on a lift(s) the next or a few days later that you hammered a day or so before.
Will they make all the difference? IMO no, but they have a catchy name.
Are they an adjunct to some already well tuned training, if you need a slight bump? Maybe