What about people who bought the game the day it released? Does it still not work that way? I can assure you that I have downloaded every single patch.
You can download the same update as many times as you want. Just delete the game data for the game and start the game, bingo! another update!
That doesn't mean the total size of the update that PD has done to the game is 1 GB. It means you have downloaded 1 GB, which is unrelated to the game's update size.