It only is if it is pre-arranged. Letting the other team win when you have zero chance anyway is not win trading. That’s just common sense. Why waste 15 minutes in a BG you’ll loose anyway, when you can just let them win in 5, and join another BG faster?
“let them win” is not as bad a Win trading, as it is to sell winns/levels through Partysynk Bg’ing Why Blizzard haven’t discovered that this is a thing, and shut off partysynk is beyond me