Uhh... I think we're misunderstanding each other here. I totally agree with what you're saying, and my reply to you was never about how all music is the same or about generalising aspects of music in general. What I'm saying is, when you're listening to an IEM, it will always impart its signature onto the music you're listening to. Now, because all music is different (like you said, synthetic instruments vs. real instruments, simulated studio environment vs. actual acoustic chambers, etc.) the reaction between the music and the IEM's signature will always be different.
For example, if I'm listening to rap music with 808 beats and a thumping bass line, an IEM with a heftier and more impactful low-end would accentuate this, making the track very fun to listen to; a positive effect IMO. On the other hand, if I use the same bassy IEM to listen to a jazz recording, suddenly the upright bass is at the forefront of the mix and the vocals are not as audible, or the tonality of the vocals become more chesty and coloured, or the piano suddenly sounds darker; a mixed or negative effect IMO.
When I'm reading Nic's reviews, they're written in such a way that they describe the IEM's signature and
not how they react to specific genres of music (most of the time at least), and so, because I can use other IEMs I'm familiar with that he's reviewed as a reference, I can infer how the IEM he's reviewing will react to my music. For example, in his Warbler Prelude review, regarding the treble he wrote, "Similar to iems as the Maestro V2 or UE18+, it’s a tuning resulting from dipping the lower treble region in order to benefit the general tone, as well the timbre of the treble itself. Even so, its warmer tone might come across as laidback, especially for listeners accustomed to brighter signatures."
Now, he could've substituted this with something like, "When listening to rock music heavily-laden with cymbals, they don't sound as exciting or energetic as something like the Jomo Samba. When listening to cellos in classical music, you won't necessarily feel the tension of the bow, but the note played will ring through with great body and tone," but that isn't as thorough and descriptive as what he actually wrote. It will leave the reader wondering, "Does that mean its treble is rolled-off? Is it merely attenuated? What part of the treble is attenuated such that it sounds that way?" Nic's reviews are written such that I can imagine what the IEM sounds like compared to other IEMs I have and think, "Oh, so the Prelude would not be as bright as my Zeus-XR, but its mid-bass has more impact, which would make it more suitable for pop music and older recordings than the XR. The XR would also be more transparent when listening to classical, while the beautiful tonality of the Prelude would make it more soulful or emotional," without Nic even having to spell it out.
In conclusion, I 1,000,000,000% agree with you that genres of music are entirely unique to one another and deliver aspects of music in very different ways. As someone who's had to record, mix, and master recordings in several different genres as college projects, part of my grade was to make sure each genre sounded distinct and to not confuse the listener by mastering my Pop project with tons of dynamic range, or compressing the crap out of my Jazz recording, or recording drums for my Rock project with minimalist mic-ing techniques, etc. It's these differences in fact, that make IEMs react differently and seem both good and bad when heard with varying genres of music. However, once you isolate the IEM's signature from the music, you can get a greater sense of whether or not you'd like the IEM based on how similar or different it is from IEMs you've heard in the past, and also estimate how well it would reproduce the music you listen to.
I sincerely hope we're not trailing off into further depths of confusion, and I wish to derail this thread no further, but I pray you see where I'm coming from
Anyways, keep me posted if you're still interested in the meet-up. Thanks 
Agreed, I'm beginning to think Nic's obsession with Astley is something more... deep-seeded. Regardless, whatever personality ends up reviewing the SE5U, I'll definitely be on the lookout.
