On a lark, I decided to try this option to grab a week's worth of updates.
The laptop rebooted immediately. Churned for a while, I could see on the console that it's trying to do updates. The laptop rebooted again, and the end result was that nothing was updated, so I just did yum update, as I always do.
Now, one thing I don't recall seeing was the wireless getting turned on during the update cycle. Which, I would think, would be a fairly important prerequisite, in order to download the updates.
Or, perhaps, I'm missing something. This laptop was updated from F17 to F18, and perhaps I need to install a package that automatically downloads updates in advance, so on update everything gets installed locally, but poking around with yum didn't find anything that seems to do that.