My 12 PM looks perfect to me until I view it side by side with my IPhone SE 2020. It’s not so much that the Pro Max looks yellow when compared to the SE, but that the SE looks bluer (and whites do look brighter).
But I also know from working with D65 calibrated monitors that those blue/cool colors are not always accurate. I’ve had phones that I thought looked warm, but were actually cooler than a D65 calibrated monitor
Since my 12 PM looks good to me except when comparing it to my SE, and it has excellent uniformity (I can’t tolerate an uneven screen tint), I will be keeping it.
Unfortunately (or maybe fortunately, for my sanity), the Apple Stores here are open by appointment only, so I can’t just walk in and compare mine to the display models.