My point is that you can't verify it, because you don't control manufacturing. Just like you can't verify that the server is running the open source code.
Maybe I can't verify those things, but a lot of people can and if anyone finds anything suspicious, they will make a lot of noise and everyone will know. This is how community verification works. It adds additional verification procedure, thus making everything in general more secure.
If you really need to be sure, you can also hire a professional and they will verify that for you, too. Try to do that with iPhone software and hardware.
