You're talking about this picture?
As it was mentioned right at the beginning of the current article
"The part was in an intermediate stage of production, and thus had not been fully processed and polished, but it still offered a good look at the device's body. "
It's also kind of obvious, the metal was way too thick to be the final shell. Another phase of aluminum milling and drilling lead to the shell we see in the current article. Everything still matches when you take into account the aluminum that was removed in this phase.
Image
I've been looking closely at every back shell leak since the beginning and aside from this unfinished one, every purported iPhone 6 shell precisely match the others in almost every way.