If we had to dispense with all the scientific discoveries that were made unexpectedly, we would be living in a very different, and much less interesting world. It has often been stated that Curiosity is not seeking life. True, but what if it finds something it wasn't seeking? Is Curiosity able to detect life? Not directly, just as Dr. Grotzinger said. It *can* detect chemical 'biosignatures' which are indicators of life. For example, if it analyzes a carbon containing compound, and finds more of the lighter isotopes of carbon than the heavier ones, this would strongly point to life. Life processes preferentially make use of the lighter isotopes. We have no better explanation for a preponderance of the lighter isotopes, than the presence of life.
Guy Webster, who made the 'won't be Earthshaking, but it will be interesting' remark is not a scientist, but a journalist or publicist,
working for JPL/NASA. I doubt that he has been apprised of the information that the science team is holding so closely at the moment. He was probably
reacting to all the public speculation about the discovery of life on Mars, and recalled that he'd been told that Curiosity wasn't seeking life, and
couldn't (directly) detect it.