Hello, I also had that problem and believe me it is present in many units, in some it is more noticeable than in others or it is present in another part of the phone. To me I passed with a replacement of an iPhone 13 Pro which sent to repair for failure of the mute button, they gave me a refurbished unit that had it in the same place as yours but not all the way only on the right side and the gap was wider, it seemed poorly mounted the screen I sent it again and a new one came with the same problem but to which long on the right side, I ended up selling the phone since I was not convinced by the quality of construction of it and returning to use an iPhone X until i buy the new iPhone 14 Pro, which is pretty good assembling since the small gap is pretty much the same around the entire phone. I can tell you that the Apple Store in the exhibition models you can appreciate that problem which as I told you in some is more noticeable and in others less, according to them it does not affect the ip certification, but aesthetically it is not according to the price we pay for these phones.
Sorry for my English