My iPhone 15 Pro Max screen isn’t as good as my 13 PM, there is a slight brightness gradient from left to right (left hand side is whiter, right hand side has a bluer tint) which is noticeable at all colour temperatures with or without TrueTone selected.
Interestingly it has become less pronounced since I first got the phone but it’s still there and I find it frustrating especially as the previous phone was so good (the best iPhone screen I’ve had and I’ve owned every generation back to the 3G).
I did have a look at one in the store and it had the same issue so maybe it’s widespread.
I guess it means I’ll upgrade in October and play the lottery again, but I will return that new device if I don’t have a satisfactory screen because I don’t believe I should have to go backwards when it comes to product quality!