He writes on he's blog that he thinks a lot of parts are recycled
You might wonder why I chose to make an iPhone 6s and not an iPhone 7. I had two reasons...
However, the other reason, which turned out to be far more important, is that iPhone 7 parts are pretty hard to come by in the markets. It’s not totally clear why this is, but I have some ideas. A lot of the parts come from recycled/broken phones, and so it would make sense that there just isn’t that much supply yet.
You might wonder why I chose to make an iPhone 6s and not an iPhone 7. I had two reasons...
However, the other reason, which turned out to be far more important, is that iPhone 7 parts are pretty hard to come by in the markets. It’s not totally clear why this is, but I have some ideas. A lot of the parts come from recycled/broken phones, and so it would make sense that there just isn’t that much supply yet.
https://strangeparts.com/how-i-made-my-own-iphone-in-china/