I suspect it is most likely part of the linux freeze, actually -- which means it is probably yanked from the configuration of Kovid's build machine.
Just like the builtin file browser, which you see when using Add Books (it is ugly, and has no labels for removable drives).
The reason I don't see any of this, is because I built calibre myself, from source. I do that because it is easy to keep up-to-date

just issue a `git pull` and occasionally if any C++ files changed, `python2 setup.py build`
So no funky cursors or file browsers had a chance to make their way onto my computer.