Playing pre-recorded audio tracks is computationally the LEAST EXPENSIVE operation you can do with audio. Every DAW allows you to render to audio every track in order to reduce CPU load and hence let your computer play more tracks than it would otherwise be possible. This of course has huge downsides (and is therefore a last resort decision when you run out of better options). When you lose the midi to audio real time computation, you are stuck with a fixed outcome you cannot anymore modify, neither in real time, nor once for all at the beginning.
You cannot change the patch, the sound parameters (filter, ADSR, .....), effects, note velocity, tempo, ... whatever! It is like having a few CDs vs a real instrument. With the CDs you can listen over and over again to the same immutable songs; with the instrument you can play all the songs you want, with no limits.
At least with a DAW, although inconvenient, you can change the parameters and re-render the track(s) to audio. With a Ketron arranger you can NOT send the arranger back to Ketron and have it reflashed with the new parameters. Can you? Would it be convenient?
Is this a "HUGE leap forward in today's technology"? I do not think so. It sounds more like a two steps back from 1980's technology.

Additionally it is not clear how many audio patterns you have (I think this is intentional, not to scare potential buyers). In a midi based arranger you have not less than 20 chord shapes x 12 keys x 3 inversions x 4 variations x 8 parts x 500 styles x 1000 sounds x countless effects x all the tweaks you want apply to each parameter.
You can make all the multiplications and have an idea. How many choices do you have with Ketron audio tracks?

And even worse, if I am playing a C chord (C + E + G) and then I play (G + C + E) do I hear something happening or not? And then if a play (G# + C + E) is there something happening or not? If I change the tempo from 100 bpm to 50 bpm or 150 bpm what happens? If I want to experiment with more/less distortion to the guitar? If I want a chorused clean guitar (+ delay) instead of a distorted one?

Every midi based arranger can easily cope with all this, I would like to HEAR the audio output of a Ketron arranger (while featuring the advertised audio tracks) in these basic scenarios.