A negative behavior which suddenly appears in the 13th version of the OS certainly looks like a bug to me.
Quite possibly true. Lots of people report problems on websites but never bother to file feedback reports to Apple. If a system is replace in the UK due to a problem I very much doubt that it would be of any use given the (hundreds, thousands?) of systems that are replaced every day worldwide. I assume that there is some QC group which is tasked to find common problems so that they can be fixed in production. They aren't going to see the issue until it is reported in X number of failures. No reports, no discovery, no fixes.
If the slow directory display on large folders had always been the case in earlier versions of macOS, nobody would notice. They'd just figure that this is the way it is and must be. But, that's not the history.
Generally, bugs happen because of some change in the code in the system. It's not as if they spontaneously appear out of the blue. What you reported in your initial post to this thread, and lots of people including me also observed and reported, is pretty blatant. It's not some subtle event that requires a strange combination of hardware and software apps. It happens with stock Apple applications, like the Finder! You might even think that it would be encountered in routine regression testing, especially after well more than a year of alphas, betas, and actual field deployment.
How do we know that Apple considers this negative behavior? They don't say a word about it either way. Sometimes it appears that they half-deprecate a feature or behavior without saying anything. Perhaps they want to, ahh, encourage the use of APFS formatted drives for security reasons. They don't tell us their strategies on things. I'm not saying they should, but often it might be helpful. In this case, a couple sentences somewhere on the Apple website would save people whining about the problem with on websites and through their customer help system. That's if this is really a deliberate design decision and not an actual bug that's being ignored. Apple's consistent silence about pretty much everything not only helps with product surprises but also could be a way to manage things they don't want to deal with.
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Several of the people who reported the iMac problem on various websites, including this one, claimed to have reported the problem to Apple. They all certainly went through the Apple help system - that's how they got the responses they did from the help line people. Obviously, the owner who got his iMac replaced by Apple reported something to somebody. And, the UK Apple people seemed to have known about the problem. Are you saying that Apple engineering doesn't read reports from the people staffing the various means of contacting them?
