To each their own. I listen to mostly synthesized stuff, so I can't really judge people based on their music preferences. I mostly check out his stuff to see if something I'm interested in has glaring flaws so I can temper my expectations accordingly. He's also one of the rare reviewers to actually graph pretty much everything he reviews, which is nice. Still, I basically never take anyone's word as gospel since everyone has different ears, different preferences, and different needs from their audio gear. The TRI i3 does graph weird everywhere I see it, but for certain genre of music this is irrelevant. It's useful to know what people who make these reviews are listening for and he actually does make an effort to explain what kinds of sounds he's using in these tracks to make his assessments of the IEMs he's reviewing. As for his library, well, we could go into a music theory debate about whether rap can be legitimately classed as 'music' or not, but that would just upset people and it has no realistic impact on my life.
So yes, your determination that graphs and reviews can be broadly taken with enough salt to kill am elephant is a fair one to come to. Graphs are challenging to make when you're having to place the IEM millimeters away from the transducer, so there's plenty of opportunity for them to lie to you, especially in the upper treble where it matters. Reviewers can be authentic about how they perceive the merits or demerits of a set and it still not be relevant to you or your needs. What it can do, however, is provide another point of reference from which you can make an informed judgement about a set before you make the plunge to buy it yourself.