Welp, blame Wikipedia for that one. I'll fix it right away.The word urbe, urbis (later Latin orbe, orbis) is polysemantic. It can mean either world or city. When the name of the city was not mentioned, everybody understood that the city referred to was Rome, the City. Therefore, Restitutor Urbis (or Orbis) almost certainly meant Restorer of Rome, not of the World.
Source: I studied Latin for 3 years and I continue to read Latin to this day as I like it very much.