Man I just got mine today. Bummed seeing this.
I got my display back. So within 3 business days they actually replaced the panel which is a great outcome.
As mentioned earlier, I have 2 ASDs and I noticed the issue with both. One of them was more severe than the other.
Because I couldn't physically bring both monitors I only took one to the Apple Store, and the whole thing was quite silly. They made me feel like I was trying to negotiate something, and definitely making me feel like I was being picky. The Apple staff assigned to me was saying that he couldn't see the difference in colour... That "it's all grey...". Then, he ran some software tests with prompts asking him whether he was seeing Dead pixels, to which he kept responding no.
His manager came at some point, and had the brilliant idea to suggest to look at the ASD they had in display. Claiming that if the bleeding was the same, then it's just what I should expect from this monitor.
I did mention at some point that if it was a 300gbp monitor I wouldn't be bothered with such issue, but given the price I expect colour uniformity. To which he replied that maybe this is as good as the ASD gets, and if I want a better monitor, Apple offers a display called the XDR...
Finally, the manager went for his lunch break. The other staff started to see some differences between the edges and the rest of the screen and was ok to get it replaced.
My new panel is now fine.
I have to do another trip for the second monitor... but they discouraged me quite a lot...
Also, when I got back the other one, I asked if I could take Apple Care as originally I did not expect to have any issues just like my experience with the Thunderbolt Display, they said it's too late...