We can also go by the fact that Apple has used single 1 GB chips in the past, including in the iPhone 6, and there doesn't seem to be any reason for them to suddenly switch to two 512 GB chips
Also it would be strange for the benchmarks to get it wrong when they're obviously reading system values (as opposed to software that sometimes comes out after a device is released that just looks up the device type and makes a hard coded assumption based on that).
Right. You assume, but you didn't get that informati from this teardown. All we have is a part number and 2 chips. Then we can deduce what this means.
This post seems to say that ifixit confirmed it was 2GB which isn't true.