Both are marked as “Read Only (lower L corner)” but I assume that this is because the “Macintosh HD” designation applies to both the Read Only system and the “separate” volume containing my users, etc.

Is there anything wrong with having duplicate icons like this? Is there some way I should try to delete one of them, and how would I know which one to delete. I’m assuming, actually, that the Mac wouldn’t let me do it, because the portion of Macintosh HD that contains the System IS read only.

Seems to me Apple hasn’t really figured out an easily understandable way to describe the immutable and changeable portions of the boot volume in the Finder UI in Catalina.