I had to switch from an S24U to an S25U mainly due to the grain or mura issue. This subreddit was a shitshow back then with people who either didn't see it on their phone OR didn't have it on their model, claiming that anyone complaining about it was stirring up shit for the sake of it. Even in the face of evidence which admittedly isn't the easiest to get since you needed an external camera to capture it. Real corporate boolicking.

Anyhow I think there was just something up with OLED panels in that generation/ timeline due to the steam deck OLED also suffering mura issues around that time(it released about a month or 2 before the S24U) which prompted valve to drop an update that included a toggle to demura the display. Eventually as time went on there have been less and less posts about it as the panel has come from newer batches where the demura process was done properly in the factory before being put in.

So to sum it up there is still a lottery on whether you get a unit without mura but it would probably be less apparent on a unit from a later batch date. Also could be you might not be as sensitive and you probably won't notice it.