I hope that helps dissipate some of the fog surrounding APFS volumes.

Before I forget it, congratulations on getting Catalina up and running. It is highly likely you will have more questions in the future because of all the changes; don't hesitate to ask when they come up.

I have two requests for you...
  1. MacOS updates (ie. MacOS 10.15.4 to MacOS 10.15.5) come along every month to six weeks. Please install them as soon as they are available. These will invariably fix bugs, improve security, and sometimes add new features.
  2. MacOS upgrades (ie. Mac OS 10.15 to MacOS 11) come along annually. Please install them when they come out. These may include substantial changes in the system and may break older, no longer supported apps, but putting them off makes the next jump that much bigger and your learning curve that much steeper. I don't think you, Artie, or I want to go through this exercise again.

That said, thanks for the challenge. I enjoyed coming up with a rock-solid solution to a complex operation that could be carried out by "an intelligent but uninformed" individual such as yourself. Challenges like this keep me intellectually stimulated and helps prevent my making too many assumptions that always get me into trouble. 😜.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein