Dear BlkNotes,
I am listening right now to the songs you singled out and here is my humble opinion: even if I am not familiar with the G70, in the past I had a Roland VA7 and, given the similarities between those arrangers, I think I can say, for example, that in "Roger Rabbit" the piano backing is part of the style and is not played by the left hand of the player, who just keeps pressing the notes of the chords.
Speaking now of "Samba pa ti", I remember that in my VA7 the kind of tricks you hear done by the distorted guitar could easily be done via aftertouch, without having to use the joystick. In other words, you could route the aftertouch to control the tone and this would enable you to have that "bending effect" just pressing the key a little more. From this point of view, Roland arrangers are far more effective than -say- Yamaha.
Finally, as far as the organ riff goes, let's not forget that the G 70 is a 76 notes keyboard, so you could easily set a split point that would allow you to play the guitar part (which has a limited extension, btw) on the right side and also play a two-handed organ part in the left side of the keyboard. If you listen carefully, you will notice that the last note played by the guitar before the organ riff sounds truncated, like the player had to "hurry up" to the left, to play the organ.
So -yes- I think that it's possible that our friend (Maurice?) has actually played these songs in real time.
My only complaint, as I stated before, is the sound quality, at times poor due to distortion, but on the other hand I have to say that this was the first time that I had the opportunity to hear songs recorded with the G 70 "in the real world", in other words without all those "tricks" that we are accustomed to hear in the demo's made by Roland, Yamaha, Korg, etc, whose main purpose is to "fool us" into believing that we could do the same, once we buy the keyboard.