Hello.
Of course, if we change the option in "Settings -> Content settings" we allow the user, who returned to the website, to upload same videos again. But in this case we allow many other users to re-upload the material, removed earlier (for example per DMCA requests). The "Settings -> Content settings -> Videos with duplicate source files: Disallow" is a perfect protection from reuploading of the removed content by DMCA, but with this option a removing the user who has videos and sent an account removal request we won't allow this user to upload his videos again if he will be back to website.