@bo1972
So here is the thing. Even when talking about the "realism" of instruments.
I would make the argument that anything amplified - ultimately doesn't have much "3d" sound. Electric Guitar/Bass in particular. Anytime you are at a concert which is amplified, regardless of genre it doesn't matter. It's being pushed through amps firing in one direction, fed to a PA system.
Now, a small venue, piano, acoustic instruments, horns, etc.. Unamplified music, a singer in a small venue etc. I can buy some 3d realism to that. But, the soundwaves are still subject to the space they are in. But take out the amp/PA system I do think there is some 3d realism to acoustic instuments.
An amp - really just sends along the signal recorded. Now do some amps add some bloom - sure, but it's just sending along the signal it receives. I will grant that very, very few amps truly are neutral.
But for 3d realism, I would argue that the source (recording and whatever is passing that along), along with the speakers and the room they are in that make the biggest difference in any 3d illusion given. Obviously, the pre-amp and amp CAN flavor that, but really what you are looking for is a tremendous source, a pre and amp that impart nothing, and killer speakers and a killer room.
Now, a killer recording can help you imagine where the individual players are in a given recording. We all find that cool.
So, not sure if this has much to do with Pass strengths or weaknesses. Just decided to start typing some thoughts on this... I'm on record liking my Pass Amp and do not think it's dead neutral. I do however really like it.