The 'only' thing that really matters here is the programming. ARR changed entirely in that regard, and it doesn't matter in the slightest how much of the conceptual game transferred from 1.0, because it all had to be recreated from the ground up, which takes time, testing, and implementation. They can't actually 'use' any of the resources from 1.0 anymore then they could pull premade resources from XI.
So as much as we'd like to think of 2.0 as just an expansion of 1.0, technology just doesn't work that way.