Not quite. That section says the GM determines if it's possible, which goes back to the normal play loop. If they GM determines it's uncertain and calls for a roll, then the implication is strongly that a success will improve attitude. Or, the implication that success should be honored is as strong as it is for any other ability check, which is to say not very strong. You'll note that the rules don't actually suggest that the GM is bound by the result of the called for check, only that one is made and the GM then determines the outcome. A sad bit of oversight, if you ask my opinion.