Not sure about faulty units, though a forum member did also state that they had a slight faulty iPhone this time round and they were advised to return theirs now and await a replacement which wasn’t instantInteresting. Don’t apple do simple exchanges anymore?
Meaning, I remember years ago when i pre ordered the iPhone 5 at launch in black, then a lot of complaints came out that the chamfered edges were easy to chip/scratch, so still within the return period, i called Apple Store and arranged an exchange for the silver. They then proceeded to send me a new phone and all i had to do was return the black one. I thought apple kept surplus stock for reasons like this.