It is not so surprising. Like Roland, Korg is proud to explain how they use "sound modeling", not "sampling" to generate accordion sounds. This is how digital pianos produced piano sound 25 to 30 years ago (if not more...). Nowadays the pianos sample the sound of high-end acoustic pianos, and not surprising they sound just like the pianos that were sampled. That can be a good thing (my Yamaha sounds like a Yamaha grand, which I like) or a bad thing (the Kawai digital piano sounds just like a Kawai grand piano...). Companies like Roland and Korg have a problem here: they do not make their own acoustic pianos they could sample. They did at some point reach an agreement to sample the sound of a Fazioli grand piano. That Roland sounded great, if you like the somewhat special sound of the Fazioli piano. Now they face the same problem with accordions, because they don't make acoustic accordions. Initially I was hoping that the Bugari Evo would have the sound of high-end Bugari accordions sampled... but alas for some reason Roland didn't let them do that.
The reality is that the way an accordion really produces sound is too complex (and also different between accordions) to have an accurate model to use in the Roland or Korg accordions. They manage to include aspects of an accordion like keyboard noise, valve noise, growl and several other things, but they still do not manage to capture fully the "tone" itself. Personally the first demos (which include very little that's played on a simple single M register) do indicate that the sound is really better on the Korg, compared to the Roland, but even the Korg still does not capture how a good acoustic accordion really sounds. From what I heard so far the Stradella bass sound is a lot better than that of the Roland. The righthand side is better, but I wish it were still better.