Allan -
The answers to your first three questions are:
- Yes, Windows 10 sees the drive in File Explorer, but that is all. Can not open the drive.
- YES! I have had experience with using WD utilities and erased and reformatted the drive with Apple Disk Utilities.
- Below is taken from the About This Mac:
I tried the drive with different cable on different USB ports.
It says that it is formatted with MS-DOS FAT32, but when I erased, it said GUID and APFS in Disk Utilities.

This screen shot is from Info on the the right hand side of Disk Utilities:

- The Capacity and Used space are exactly the same...to every "bit"! Not correct. I believe I at one time saw the drive to have something in the vicinity of 250MB of TimeMachine BUs.
- The backups...three from Monterey and about five from Ventura, based on the dates and times of the backups. I had erased the drive before doing the first backup of Monterey, before upgrading. I did the upgrade the following day.
There were several times, in between the many calls to Apple Tech & Seniors, that the disk drive (entitled "MacMini M1 TMBU") popped up on the desk top. If I double clicked on the drive, I would get the BBOD. However, opening the Finder window and clicking on the TMBU in the left side bar, it would open and I would see the several dates and back-ups from both OSes, though I only cared about the second one to down-grade back to Monterey. Also, a couple of times the drive would also be found by Migration Assistant. However, when it went exploring to find what application and documents to migrate, it would search for hours. I even let it go 12 hours and nothing happened. Had I known then (even told by some techs you can't) I could have dragged my data files over, I would have when I saw the folders and files on the TMBU disk. GRRRR!
That's the short answer to your questions. I know what you mean about the Black drives, if they are the ones called MyBook, MyBookLive and MyBookWorld (white). I have them all. The MyBookLive (original one)Is on my network as a NAS drive. My MBP has been doing TMBUs to it for years. I tried to figure out how to ** my MacMini M1 to it, but all I could determine was that the drive had to be erased and reformatted. Not willing to do that as there are also files on it from my Windows machine. Knock on wood, that it continues to behave until I get a chance to perhaps get the new MyBookLive.
Thank you for your questions and help in figuring this all out. The Utilities report are puzzling as they do not reflect what I am 99% certain they should say.
Best, Jim