Does this flaw impact the camera function? That's a sincere question because I honestly don't know. That is the only condition under which I would deem this to be a defect that requires replacement.
I am no Apple apologist, but expecting your device to be "flawless" is an impossible pipe dream. These are not works of art, they are phones, for crying out loud. I know Apple brings it on themselves by appearing to cater to the OCD population exclusively, but you will never be satisfied if such minor imperfections result in 10 replacement phones.