It's not called out specifically in the prose of article, but I think the dimensions overlaid on the image show quite a bit of intentional space left for tolerance around the sides of the battery, and they mention the walls formed by the aluminum carrier around the battery pack. This is pretty clearly intentional "walling off" of the battery from the rest of the PCB, and (I assume) is more protection than other devices were designed with.

If my assumption is correct, though, I find it strange that article footnote seems to contradict this by essentially saying the engineers didn't give enough space around the 'front' and 'back' of the battery. Did they protect the PCB and battery from each other, and fail to protect the battery from the front and back of the phone?