Well, Roland announce it as if no body else offer those editing features in any arranger. No true.
In the korg TOL arrangers (PA2x, PA1x, PA800, PA3x) you can do all of those editing and more. Is new to the Prelude, but no new to other arrangers.
Some of those editing you can do it in the Audya too. Want to stop the backing tracks, just hit stop/start, plus you have the sliders anyway.
In the arranger world only about 10% of the users do detail editing anyway.