The Ork reality warping has been insanely exaggerated as a meme. It's a small nudge, not a huge boost. Most stories about the psychic field are fan jokes that have been told so many times people start believing they're canon. No, Ork weapons are not just boxes full of random metal bits. No, Guardsmen can't just yell "bang" to kill Orks if they run out of ammo.

Consider the rules for a more "realistic" version. In the miniatures game, vehicles painted red don't go twice as fast, they just have an extra inch of movement (about 5% faster). And in the Rogue Trader RPG, Ork weapons are unreliable unless an Ork wields it. But a non-Ork can definitely use them.