Per Roland, sets are designed to represent different kinds of accordions from the factory (I think the factory has like 50 different kinds of accordions), while UPG are exactly what their name us USER PROGRAMABLE. It is a series of up to 1400 individual Justin sound registratons (accordion/other instruments together or individual), that we as owners of the 8X can change to our heart's content. Here is the nice part, we can modify the sets too, which gives the V-accordion a range of sonic options not possible on any other digital accordion in the world.
The one place that Roland is globally useless in is their manuals, they are pretty much good for nothing except telling you what the tech specs are (but never clearly explain what they do), for all their products, but in the case of the 8X, it is REALLY of no practical use at all, which is why I started to make the FR-8X Mild to Wild Series of videos.
Too bad that Roland doesn't care enough about it to advance the project.