I think this post from Reddit sums up what many are trying to illustrate since the design change of the IPhone 12/13's:
"The gap tolerance has to remain that way, that’s how they’re able to remove and replace your display if it gets cracked.
Also, glass/ceramic hybrid materials expand and contract with temperature fluctuations, so where the glass meets the chassis, it can’t be completely flush, otherwise the material will crack...much in the same way a skyscraper has to be able to sway in the wind...if it can’t, it will break."
Bottom line is gaps are there in the frame whether you know it or not....obviously some more apparent than others. Its a non-issue. If you want to take the chance in playing the return game, do what makes you happy. There is a very good chance you end up with this problem again in addition to something else judging by how bad Apple QC is anymore with chips, scratches, bad screens, scratches on screens, dust in the camera lenses all coming new out of the box.