classical label monitors

Are you suggesting that the studio engineer expects the mix they settle on, to sound predictably different on playback, than what they hear initially? I gather the ATCs are not made for listening and are very analytical compared to a home stereo. Certainly they take into account some preconceived typical speaker voicing. I can't think of why they wouldn't use similiar sounding speakers albeit nearfield etc.
I have read here and elsewhere that they record for playback in a car. Then it would make more sense, I suppose, for them to emulate an average automobile's audio system/acoustics (while running) to make the best mix. Classical music may not be lumped into that thinking.

Perusing pro-audio magazines, books, and web sites it appears that the qualities searched for in a monitor include (1) accuracy (2) resolution so as not to miss flaws (3) reproducible settings when working with the same monitor in another setting and (4) lack of fatigue - so that one can work for many hours.

I see B&W mentioned a lot in CD booklets.

It depends upon the type of music being mixed and assumptions about how it will be played back. For classical it's usually mixed for accuracy. It's similar for jazz. For pop, rap, modern country it can be very different and "compromise" mixes are more common. Remember, large amounts of music is now experienced in a digitally compressed format, a digitally compressed format accompanying video on a computer, thru very cheap headphones, as part of a video game, etc. It really doesn't make that much sense for an artist/producer/engineer to produce highly dynamic, wide frequency music when that's the case.