This is just pure guess with some educated knowledge . An inverted W is bad because it puts significant stretch on the arm and shoulders before muscle contraction for the throw. Some coaches talk about separating ball-glove with thumb down, which will give you the invert W. (You get less shoulder internal rotation in a horizontal W than an inverted W). Inverted W will proved extra arm power because you put your shoulder at full internal rotation and shortened the internal rotation rubber band (muscles and tendons) then you quickly externally rotated the shoulder on a short rubber band and fire.
A short vs long rubber band stretched the same distance will yield greater force from the short one. But more ware and tear. If your not throwing at 100% maybe it's ok.
Again this is only guess work