Again, I think you are chasing this idea without having read Toole. It has been investigated and the result is not what you (repeatedly) say.
I don't think Toole nor Olive are saying that the most neutral sound is always prefred. Perhaps they are saying that it is surprisingly often that it is prefered. I certainly want creators of content to use neutral speakers.
Anyway I'd like to see them run these tests again someday with better controls for what aspects of sound are generating the scores.
Look at the variation in bass preference. Yikes.
Not to mention many folks prefer some bass & trebble boost at lower volumes. Likely due to how we percive these ranges at lower vs high volumes. So perceived neutrality is likely SPL dependent.
Actually I have yet to read of any study that was testing this using contemporary technologies. Such as using the exact same speaker with different PEQ applied so the only major variation was level of frequency neutrality. This is something some of us can do at home using a speaker that responds well to EQ. Much easier than speaker swapping.
I did a very informal version of this with my GF and need to do more. I will say in this test she actually prefered a less neutral sound to the PEQ'd toward neutral sound of the Polk T50.
We also compared two speakers with the same Harman score and one was prefred dramatically more than the other, not even close. (The H score was the same but they did measure very differently in some ways)
In any case as a hobbyist I am no expert. I would love to be involved in a well conducted series of tests run by experts.
Anyway after exploring a huge number of speakers over the last couple years and making a few designs myself I have to say I was surprised at how much variation there was in personal enjoyment of the various speakers. While most sounded good enough to qualify as nice speakers some just caused me to want to listen more, to eat the music up.
I was also surprise at how slight tweaks really changed my level of listening enjoyment over longer sessions and yet in shorter sessions those tweaks might go unnoticed.(small frequency adjustments on my DIY attempts and slight variations of xover points, plus room EQ really changed the game - not talking about power cables, tube connectors or such type of "tweaks")
They will use neutral sounding studio monitoring and will listen to what’s been laid down. If you look at photos or videos of recordings being made, they are listening and adjusting the recorded sound as they prefer it to be. All the equipment they use will have been rigorously measured and tested when being built and installed. The final judgement on what they think the recording should sound like is based on what they hear. So regardless of how well your domestic equipment is measured and tested you will only hear a subjective take on the music or home cinema you listen too.
Kudos to the ones using netral speakers yet many studios it would seem are actually not using neutral speakers nor anything even close to SOTA speakers.
So you have that subjective cut made on speakers that would not measure well in the 1st place.
You simply can not remove subjectivity.
Producers and studio people are artists.