...
The EC download/patching is handled MUCH differently than the 2d version.
The 2d version starts at whatever client version (say Version A) that you install then downloads each separate patch and installs then, so it goes:
Version A installed
Download Version B and install
Download Version C and install...
...
Until you reach the latest patch/build of the client.
The EC starts with a base set of files when installed, then does a ONE TIME download of the latest build of the client.
So basically, a patch up from a new install for the EC will always be the 2 gig download, depending on the build of the 2d client that is hosted, the 2d client can have a larger and longer patch process.