Oh, I thought everyone is familiar with that work from Dr. Sean Olive. See:
http://seanolive.blogspot.com/2008/12/part-2-differences-in-performances-of.html
It is reliability factor of listeners when performing listening tests of speakers. See my video here:
Yes I have seen that. EVERYONE has seen that. All the "serious" reviewers have seen it, I'm not talking about the 2m sub youtubers who cover tech - I'm talking about the ones on that squidly link and Crinacle, etc. All the manufacturers have seen it too.
Consider this:
All of the manufacturers are familiar with the Toole/Olive research and the Harman curve.
Most of the manufacturers have a line of 5-10 IEMs, different models and usually at least one of their models (past or present) conforms very closely to the Harman curve.
If the research was an accurate representation of consumer preference then by now the market would have spoken very clearly; IEMs which matched the Harman curve would dramatically outsell those that did not and the only remaining models would be those that matched this research.
We have data points from millions of consumers and tens or hundreds of thousands of "serious" IEM users - those obsessively into it as a hobby who all own many sets, and musicians and DJs who use them professionally.
The Harman curve conforming IEMs are NOT the best selling ones. The research doesn't match the real world data generated across vastly larger sample sizes as shown by purchasing decisions over the last couple of decades.
Why hasn't JBL simply dominated the IEM market and driven all the other manufacturers out of business? Do you really think Sony, Sennheiser, etc. haven't done their own research?
You can't escape this fact by deriding "stupid" consumers either, they were the source of the data that fed into Harman curve in the first place.
At the very least you don't seem to understand that manufacturers of $2,000 IEMs are not aiming at the general consumer target market, in the same way as Ferrari don't pay slavish attention to the research which drives the development of the Toyota Corolla.
The hobbyist/professional IEM market (as distinct from the general planet-wide market) has room for variation, different models appeal to people who may find themselves not exactly aligned with the Harman preference curve. This market is easily in the tens of thousands, likely many hundreds of thousands of units shipped annually, the majority in China.
So a review of a $2,000 set complaining about deviance from the Harman curve as though they simply don't get it is like a review of a Ferrari complaining about the difficulty of getting a child seat fitted.
