Except that nullable types aren't the same thing as option types, so it's not doing the same thing. Nullables are much weaker than options. You can't do this for instance:

    string? id = "Name";

While you can do stuff like this:

   int x = 0;
   int? y = x;

Again, F# has nullable types and options, and the fact that no one in F# uses nullable types should tell you something.