Following a little more exploration, I have located the path to the macOS version database in recent and current macOS Catalina betas. I therefore offer an updated release of my utility for working with document versions, Revisionist. This now reports the size of the existing version database correctly, in its Browser window. There are no other changes.
Revisionist version 1.6 is now available from here: revisionist16
from Downloads above, from its Product Page, and through the self-update mechanism in previous versions.