so, I was thinking about all these mechanics that are good or bad and that kind of popped out from nowhere and i believe it might make sense. a lot of bad pitching mechanics that are thaught by coaches might be fielders mechanics. Be aware that it's just speculation because i'm nophysiologist or anything.
showing the ball to centerfield: that might be used to reduce movement on the ball since you won't pronate as much when you throw it.
doing the inverted W: I believe it might gives you a couple MPHs on your fastball since most people doing it will start rotating their shoulders with a horizontal arm which maximize the forearm bounce back. that is something bad for a pitcher thought because that puts extra stress on your elbow/shoulders but lets say an outfielder that throws about 10 times a game, it doesn't have that much effect.
there is probably a couple others but i can't think about it now.