Jehovah's Witnesses, why does an Evangelical pastor/scholar agree that Jesus was not hanged on a "cross"?

"When it comes to the individual terms, some conclusions can be drawn. A σταυρός is a pole in the broadest sense. It is not the equivalent of a 'cross' (†). In some cases, it is a kind of suspension device, used for the suspension of corpses, torture or in a few cases executionary suspensions. Very little or nothing is said about what it was made of or how it looked." -- Gunnar Samuelsson, "Crucifixion in Antiquity: An Inquiry into the Background of the New Testament Terminology of Crucifixion" (Gothenburg University, 2010)