I live in China and my city, Xiamen, has one of the only official Apple stores in China. I went in to buy a 3rd Gen iPad Air and they had no 256gb in stock. I found a very high rated/reputable seller on taobao (kind of like our eBay) and purchased one, Space Grey 256gb. I took it into the Apple store after receiving it to get a diagnostic done to make sure it was legit. We looked up the serial number and Apparently it was a genuine 64gb Air 3 purchased from Amazon that had been modified to 256gb. The diagnostic at the Apple store showed everything works perfectly and I have had no issues with Siri or App Store. The Apple Pencil works fine. Swiping gestures work flawlessly. The Genius Bar guy that helped me said it looks like it should be fine, it was a well done modification. Should I return it or just use it as is? Everything works smoothly.