When I said pronated or supinated, I was referring to the motion, not necessarily the arm.
If a neutral stroke (one that is unescaped on both sides) is considered “neutral” stroke, then what else are you going to use to convey a different stroke trajectory?
If a player starts with a neutral stroke and then supinates his forearm, he now has a downward (supinated) stroke. If a player starts with a neutral stroke and pronates his forearm, he new has an upward (pronated) stroke.
(Relative) Pronation and supination of the forearm is what controls the angle of the stroke. Pronation or supination of the wrist has little to do with it.