Been running the exact same tests on my account today (before I saw your post).
Got the same strange results and did sweat a bit!
I don't really understand why there is a 'Empty trash' button if the files are not directly and permanently deleted!
On this page: https://www.idrive.com/help/Windows/trash
it states: Delete: 'Delete files permanently from Trash' ...
Anyway, thanks for the info.