Well, I'm intrigued as to what you think the fault actually is. Given that the backlight clearly stretches all the way to the very edges of the bezel for all of us, the only variable is the rubber seal that it's shining 'through'. It looks like
incredibly small inconsistencies in the straightness or thickness of that seal to me, which – given the nature of manufacturing – are inevitable. Are you expecting all the keys on the keyboard to have absolutely no lateral movement to them as well?
I'd have to see one that didn't have the 'issue' with my own eyes to believe it, tbh. We're hardly testing under controlled conditions here, are we?
And comparing it to other laptops is obviously irrelevant.
Like I say, I expect you'll be disappointed in your replacement.