I don't think that getting a only a couple of responses indicating a problem can really be called 'a lottery on these screens'. If this thread were to be taken as a scientific representation, it would strongly suggest there is not a problem, or barely a problem.
Of course it isn't a scientific representation, but having basically invited every M1 iMac owner who visits macrumors to check their screens, it isn't a surprise that there are some who will notice an issue. There is no such thing as perfection.
Realistically, according to reviewers and commentators so far at least, the 24-inch iMac screen is the best display of its type - at least anywhere near the price. I might be wrong, but that does quite literally mean 'best quality', so far at least. It doesn't mean perfect however.