I recently went through five ASUS PG279Q monitors, every single one of them had massive white uniformity issues. Basically there were yellow-tinted patches on the screen which you could easily spot, as shown on this image:
https://imgur.com/nYcpLQa
People said that this is a known issue of the AU Optronics panels, but apparently Acer (who uses the same panels) has better quality control so you're less likely to get a defective unit... so I bought the XB271HU and... it's the same issue. Granted, it's to a lesser extent, the discolored patch is in the upper-right quadrant, but it's still there. When I scroll a page with bright backgrounds and follow one spot with my eyes, I can see how it changes from brighter warmer tint in the upper area compared to the lower area and the whole far right side has a much cooler/darker tint. Here's how it looks like:
https://imgur.com/xdyoIaX
My question is - do you have these issues too? It looks like everybody keeps focusing on the backlight bleed, yet none of those 5 ASUS monitors or this Acer had any bleed, but all were non-uniform. Did you check for uniformity? I know it's a "gaming" screen and you may not notice it in gaming, but when you open a website with white or gray background or scroll through your mails in Gmail, do you see the change in color temperature either left-to-right or top-to-bottom? I wonder whether a uniform high-speed IPS panel even exists.
FAQ & Answers
This is simply because they don't really include uniformity tests in the QC - or, actually, they rather relaxed (simple 9-point measurement +-20% I believe, at least from datasheets I've seen).
For these market segments (gaming, home consumer) its considered that majority of customer base does not care about solid colour uniformity anyway - because they mostly watch movies, play games or display some picture on it when you don't notice it.
If you want monitor with panel graded for uniformity, you need to go into pro or high-end business segment (just don't go for ASUS or Acer since their "pro" models are simple re badge and no sane professional would consider them).
Generally, larger the screen, more chance to get one with uniformity problems. Does not mean you will get one - as you've mentioned you had lot of screens before that were just fine.
I am simply stating the fact that ultimately what is a "defect" is what was not as promised. You can't say that panel is defective if 100% perfect uniformity (or even 90% uniformity) wasn't specced in first place.
The unfortunate realities of modern monitor & panel market, sadly. Throwing away panels with uniformity issues is expensive and monitor manufacturers are not doing it simply because they prefer to accept some returns (later finding less picky buyers for refurbs).