I don't think it's small potatoes that the iPhone is being bested in the camera department. Yes, it's true to say that that doesn't mean the iPhone camera is bad (that'd be a foolish argument), but it's also true to say it matters that other smartphones are topping it. The iPhone has long been heralded as the smartphone with the greatest camera. One that chips away at the need for point and shoots, and even some arguing rivaling or at least knocking on the door of DSR's -- debatable, of course, but the point is, that's how good the iPhone camera was always made out to be.
It's another item to add to the list. In the past couple of years, the screen, battery, design, and now camera have been topped by others (possibly more, but those are the few things that come to mind). These things will continue to chip away at Apple, and that isn't something any Apple fan nor Apple themselves should ignore or treat lightly. It's a testament to how far Android OEMs have come with the camera. Frankly, it's about damn time they caught up; but it's also no small feat that they've surpassed the iPhone. And it's also interesting (maybe even alarming?) that the overall score of the 6S doesn't even top the 6.
Also, in my opinion, it's not just about camera quality. It's about the camera experience, too. And having had both the S6 and iPhone 6, I can say the camera experience is far easier/better on the S6. Double-tap to launch gets me to my camera faster; the ability to customize my camera modes makes it easier to get to the specific mode I want; access to more camera settings right away makes life easier; etc. At the end of the day, it usually comes down to software experience, and it just seems almost everywhere you look, life is easier on an Android device. That's been my experience anyway across a number of things. And now, Android users can also say for certain things, it's not just easier, but also better.