You have pretty much nailed the resoning behind it
There were a lot of requests for them to be more transportable, especially the 686 as folk want to take their Epics on Holiday.
There has been a good years worth of effort gone into getting the action to translate into 4 pc, so the rods feel the same as the existing product.
I've not had the chance to try one out yet, so couldn't comment beyond Carls explanation, when i asked the same questions.
However i will hopefully see one fairly soon and can report back.
For now both 3pc and 4pc will run concurrently, but i would imagine for the future all the rods will be 4 pc.
This will make a big difference to me in Shipping costs to Europe
Fundamentally the rods are staying the same, same colours, same actions, same sizes, just the configuration thats changing.
Sandy