Nitpick: the "loudness war" is about mastering / compressing a recording so that it sounds louder at any given volume, it doesn't really have anything to do with optimizing things so they sound better at high volumes or a preference for loud sounding instruments.
I don't know. I'd argue that if the production process is influenced by the loudness war, then it too becomes part of the loudness war.
For example, a technique of masking distortion (or clipping, rather) is adding something with rich harmonic content (a trumpet for example) to parts that are expected to be hitting the wall and otherwise distorting / clipping.
Would trumpets be there otherwise? I don't know, but I'm sure producers are aware of the limitations of digital audio and as such adapt the music to it.
I worked as a mastering engineer for a couple years back in the aughts, and I can confirm that to really max things out requires production techniques.
For example, analog tape naturally saturates high frequency sounds before low frequency sounds, which brings down the peak level of a close mic'd drum. Peak limiting a recording which already has analog-saturated drums produces fewer audible artifacts.
In the abstract, at mastering-time you can achieve any absolute level without hard-clipping by smushing down the peaks with peak limiting and multi-band compression, then dialing things back up with makeup gain. But when compared against the original recording in a level matched test, at some point the processed result becomes unacceptably degraded.
