Jumping to conclusions
It is very appropriate to suggest caution before arriving at final conclusions. But it would be silly to summarily dismiss the potential implications of this find in the context of the discovery of many other deposits of olivine at the surface of Mars. Keep in mind, it is estimated that there are over one millions square miles of olivine deposits ubiquitously dispersed over the surface of Mars. This is merely one of the larger single deposits yets found. When put into this context, what we have is a Mars that has been cold and dry for billions of years. We shall see how subsequent evidence either reinforces or contradicts this data.
But if I were you, I wouldn't be jumping to conclusions that Todd Hoefen is wrong about this.