simultaneous downloads and unlinking symlinks

I have been looking through the zencart code trying to understand the process involved in creating symlinks for secure downloads. one specific part of the script actively removes the current symlinks from the public download folder before creating a new symlink (using function zen_unlink_temp_dir).

does this not cause any existing symlinks to be removed and therefore potentially could cause problems with download reliability. I wonder how the system deals with near simultaneous creation of links and the associated unlinking of the any symlinks in the folder. I am assuming that its more a case of my mis-understanding the process than a real issue.

anyone got any direct experience/knowledge of this?

cheers