I am pretty sure that the 16GB + 6GB has been misunderstood.
This was indicated by SE as the system requirements. SE has never said that the first patch will be 6GB. In fact, I would be very surprised if it is anywhere near that size given that the entire beta was not much bigger than 6GB.
The requirement has been articulated this way as when you download, the files are stored as torrents prior to being installed. My interpretation of the 16+6 is that the install will by 16gb but you will need to have additional space on your HDD for 6GB of download temporarily as somewhere to store the torrents. NOT that there will be a 6GB torrent right now but future updates might be so you need space to do them.
The last thing SE wants is to say that the game requires 16GB only to later have people complain that they cant fit the subsequent patches on their HDD.
FFXIV: Crafty Hallie, Ultros