Then I don't understand what are you talking about.

Entire game = entire client data.
Update = Only some files of the client, but could also impact all fils of the client as they are packed/Archives files and inside these archives one file of 10000 could change. If the client is not able to only update this 1 file in the big archive it needs to download the whole archive again.

So an update could also be an update of the entire game.
But we should stop to get off-topic here. The answer to the addons question was officially given, everything else will be in natch-potes or official forums.