I don't understand the operation or purpose of "clean download directories". I understand it may delete files previously downloaded, but I don't know when or why.
If space on the downloading computer is not a problem (nor space on the iso or usb stick), why would I ever want to check "clean download directories"? Couldn't I just let updates accumulate in the download directories, since what is installed on a target system is always determined by the requirements of *that* system, as determined at the time of installation?
In other words, is "clean download directories" just to save disk space, or is it to prevent the installation of old or obsolete updates?