No, its not a "much tougher" camera comared to the E M1 II. You could wash the E M1 II in tap water and have no problem, you can go into water falls taking pictures, I had no problem doing that. Working in minus 10 Celcius degrees? Done that, No problem.
Olympus always gave us impressive weather proof bodies, so I don't see any real E M1 X advantage in this area.