I wish I could. Since you have done so much testing and I've heard a lot about this bug over the years:
Do you know if it is linked to certain manufactures (WD, Seagate etc.) or just types of drives from everyone (like only 5TB self powered WD mobile drives eject but the 4TB ones are fine)?
Or is it more like: two of the same exact same drives, one has the issue and the other doesn't?
Or mobile drives are the problem and desktop drives are fine?
I will be getting a Monterey running MacBook Pro soon and I have a lot of 4TB and 5TB WD mobile drives that I can test if there is any connection to that. I'm also concerned now as well. 😱
Thanks for any answer you can give.
Perhaps
this detailed bulleted summary will be helpful to answer these questions. And there's good information in the rest of that thread too. There's also many other threads here and on other sites about this, illustrating that it's not any one cable, any one enclosure, any one bit of firmware, any one brand, any single Mac settings, any one user error, etc.
But nutshell: some devices are affected, some work fine. It SEEMS like HDD enclosures are more likely to have issues than SSD ones... and RAID HDDs seem most likely to exhibit this... but RAID SSDs are not immune. There's no brand bias/dependability: one enclosure from a brand may be fine, a different may do this. I'm not aware of any case- including for me- where 2 of the very same enclosures or drive will split with one being fine and the other having issues (I do not think that applies to this issue at all). Mobile or Desktop drives seem equally likely to have issues OR NOT... but again, SSD seems less likely vs. HDD enclosures.
I have a WD mobile HDD and generally do NOT have problems with it. But I also tend to only have it connected for brief periods and haven't left it connected for hours. I just gifted a brand new WD desk enclosure and- linked to a brand new Mac mini- it's not fully ejecting but is triggering a tall pile of notifications about "unexpected ejections" each time one comes back to do something on the Mac. This is fully a hit or miss. The U in USB may mean what it is supposed to mean with one enclosure but not with another.
I've had no issues at all with OWC Ministack STX, now reliably connected for a few years. However, another OWC enclosure (RAID HDD) won't stay connected for longer than 3 hours... UNLESS I connect it to any Mac running macOS < Big Sur or any PC and then it is as stable as it has always been (since about 2018 or so): same cable, same firmware, same drives, etc.