With steak, the intermal temperature doesn't matter. The harmful bacteria cannot penetrate the surface of the meat. As long as the outside layer comes to 160 degrees, you're fine. And the outside layer hits that temperature like 10 seconds after hitting the grill.
Hamburger and other ground beef products need to be cooked through because they are ground up and processed. The bacteria still can't penetrate beyond the outer layer of the meat, even in ground, but since that "outer layer" is all mashed through the meat during the grinding, you need to cook all of a burger or cube steak to that 160 degrees.
ZV