I don't think JSHint has a good reason to warn about this situation. I don't see anything in the specification (http://www.ecma-international.org/publications/standards/Ecma-262.htm, pages 30-31) that requires there to be a getter if there is a setter or vice versa, and it is easy to imagine a setter that doesn't imply a getter. For example, you might want to set a dirty flag in a setter. There would be no reason to define a getter.
I did not see a justification in the JSHint source, or its history.