Why are two different non-overlapping lists of files in the same iCloud (Books) folder?

I recently realized I had two copies of the same book, in the same folder, with the same name that I cannot see simultaneously in the same Finder window. Besides the fact that this should not be possible I am very confused as to how this is happening.

Two different Finder window reveals a different list of files in the same folder, and searching for the title finds both files, in the same folder.

This is perhaps best explained by the attached screenshot.

I've come to realize that one list is a partial list of books in Apple Books but I fail to understand why, or how, this is happening. More importantly, I don't understand how to manage these files, if at all, in Finder.