How can a system be judged with highly processed, non acoustic music?

I agree with your characterizations and might describe what I hear a little differently. Not sure it’s an issue of truth, but more of tradition vs more modern. A similar trend toward a certain kind of sound can be found with many manufacturers of acoustic instruments other than piano. In addition to what you describe, I would add that the Fazioli, a modern company, also has a hollowness and shouty quality that I don’t like, the Steinway (my favorite) has warmth and the best balanced sound, and the Bosendorfer is somewhere in the middle with more power than the Steinway. All great in their own way and, of course, there is the issue of feel and action which are important only to the player.

frogman -- I'll bet my memory is playing tricks on me, but I'm pretty sure that when I went to L.A.'s piano shops and played those three brands brands, it was only the Fazioli that gave me the shakes. It was only the Fazioli that compelled me to return to the dealer and drive them nuts with my horrible playing, once again.

I might want to say, too, that for a while I lived within walking distance of a very good piano store. And that I continue to love the early 20th Century, 52" Mason & Hamlin upright. I was compelled to buy it when the wife lost patience with the living room hogging Petrof Grand I'd been banging on previously.

It cannot be judged for accuracy.  Maybe timing, but not much else.  Amplified instruments do not provide an accurate point of reference sine the instruments; tone will be enslaved by the musical instruments amplifiers' distortions.  Even vocals can suffer from control-board-itis and compression.

Acoustic guitars also change over time and some are better than others, in fact much better even among the same models of the same brands. A late 30s Martin D-18? Astonishing or unplayable depending on the guitar's life over time...Richard Hoover of Santa Cruz says you gotta play the things to make 'em great.