There are seven moderators. They don't always come to the same conclusions. The system doesn't provide a way to reverse a ruling on a flag. We can go back and change the outcome (open a post that had been closed or vice versa), but the original ruling on the flag stays, even if it happened because someone clicked in the wrong place.
In this case, two volunteer moderators on two different continents who have never met each other in person read a flag on a post and came to different conclusions, without even realizing until after the fact that they disagreed with each other. What is remarkable, actually, is how consistent rulings often are.
But moderators sometimes even overrule themselves. If someone flags something, a moderator reads the flag and decides how to handle it, which might involve declining the flag. If later, the same person disagrees win the moderator's choice to decline the flag and flags the post again, the same moderator might read the second flag, be persuaded by what the person wrote, and act on it.
In this case, by the way, I believe that asking users to report the facts of their firsthand experience is the definition of "not an opinion." But I also see how the question could turn into an invitation for people to rant about how Apple ruined their phones with iOS 8, and how this is the. worst Update Ever and Never Would Have Happened If Steve Were Still Here (etc).
This is all an imprecise science, but the point is that while we can reverse what is done to a post, we cannot reverse the decision we made about whether a flag was helpful or not.