You can technically eat a ribs at 165° Fahrenheit. But this isn't doing justice to the ribs or all your hard work. At 165 degrees, you will have chewy ribs.
When you are slow cooking a ribs, the internal temperature is rising. There is a good amount of fat on the outer layer of the ribs. This is where a lot of the flavor of ribs comes from.
If you keep the ribs on until the internal temperature is 195 - °203° Fahrenheit, this will allow the fat to melt and render into the meat, but also create that firm, yet fall of the bone texture your ribs should be served at.