I owned a PSR-3000 for a while. Yamaha made some subtle, undocumented revisions to their chord recognition logic sometime before the introduction of the PSR-S910, which made it easier to play Maj7 chords on the newer models. By "easier," I mean that the revised programming allowed you to play these chords by pressing fewer keys, and they were recognized in more inversions, which translates to less hand movement.

I know you're all going to jump on me now, and say "Just practice more." "You really should be pressing all four notes for a major seventh," etc. But a programming change like this instantly allowed me to play some songs that had difficult progressions a tempo without making the usual mistakes. So for me, the programming changes justified upgrading to the newer model. Yes, the PSR-3000 had better build quality.

Yamaha also made a couple of subtle changes to its "AI Fingered" system, since that system was introduced on the original Tyros circa 2000. I believe those changes affected the repertoire of "rootless" chords. Not something I use, but I remember a few here on the forum were disappointed when they discovered this.

Yamaha doesn't document these types of changes in detail because, well, they're never wrong. They don't make mistakes, so they don't have to correct them! :-) But if they added a setting to the Genos, etc., that allowed a single note to be recognized as a MAJOR chord, instead of a unison (what were they thinking!?) then my check would be in the mail!

As an aside, I actually created a custom style for my Tyros 5, using a third-party utility to edit hidden parameters in the CASM. In the AI Fingered mode, any time you play a single note, a Unison [1+8] is recognized. However, for this chord type, I programmed my style to sound the "missing" third and fifth on unused channel tracks. So what you hear is a major chord! What did I name this special style? "Down with the Unison!"