John, the problem is that there are a lot of advanced keyboard techniques that involve using BOTH hands. When your LH is mandatorily committed to HAVING to input the chords ALL the time, there go those techniques out the window.
Sure, you say, if you want to use them, use an SMF. But there goes your interactivity, out the window. What's a boy to do?
I doubt you ever tried the old Roland Chord Sequencer, but it provided the best combination of the two systems (ARR and SMF). Seamless changeover from one form to the other. You played with the arranger, when you got to a section you wanted to solo over, you'd hit the Record button, it would record JUST the chords, hit play and it temporarily took over your chords, so you could solo two handed, play another instrument, go to the bathroom, whatever!
Hit Stop on the CS, and you were back seamlessly in normal ARR play. No-one is ever the wiser (do you honestly think that many of your audience can tell the difference between you playing in ARR mode and SMF, anyway, especially now most SMF players have Markers for jumping to different sections seamlessly?).
Now for whatever boneheaded reason, Roland stopped using this revolutionary feature (from a long list of great features they dropped!), so there has been no way, especially on a Roland, which can't sync ARR and SMF, to use these techniques. This looper, if it works as advertised, could bring back at least part of what made the CS so good, and add a few more capabilities that the old CS never could.
But unless you ever tried the old CS, John, I respectfully suggest you don't understand what it could do for you. I LOVE arranger play. I love it's interactivity, re-harmonizing and restructuring on the fly. I HATE having to play the chords for a vamp or repeated section when I want to solo two handed, if I've already played them once.
Chord Sequencer, or looper, I don't care... It's the best of BOTH worlds