It's not a software update. If you run softwareupdate -l you will not see it. It is being offered to users of qualifying machines as a free update. If you have a restricted software entry added for Mavericks, you should be fine.
Can someone assist me with creating a software restriction for Mavericks? I would like to get this done today if possible. We like to test updates before we deploy them. Unfortunately our laptop users are admins. This would be a great way to stop them from upgrading.