The claim is common; it appears, for instance, here.
I contend that this claim is itself irrational, and loss aversion makes perfect sense. Whatever I have now, I am getting by with it, and a loss of some of it might endanger my lifestyle, my family, or even my life.
Whatever I don't have now, I am getting by without it. And while getting it might seem attractive, I really don't know: perhaps it would ruin me! (Think of the curse of the lottery winner.)