Although you can if you look hard enough find some technical literature (trade journals, etc) that conflates the terms, once the "Auto wrench" arrived, trade journals and catalogs etc mainly honored the distinctions between them and monkey wrenches. It's not just a difference in industries (RR, oil rigs, heavy construction boltage vs automobile boltage), but a difference in mechanisms. Monkey wrenches are screw wrenches, Auto wrenches are not. They have a worm gear, just like bicycle wrenches. They are, in essence, overgrown bicycle wrenches.