Future (hopefully) owner here. I reviewed my friend's R10 that was refurbished by Vesper Audio here:
https://den-fi.com/sony-mdr-r10/
I believe that any headphone can’t ever be as natural as reality, because the headphones-each headphone- creates its own room of sound, which then may or not can enjoy the listener,but instead the reality, that the environment in which you sound varies from context to context, the headphone obviously has its own static environment,while the speakers can be placed in more or less large rooms and determine a different sound room, more open and therefore more "alive". Where I, like many other headphones (like you), determine the naturalness of the headphones, is in its timbre .and the R10 makes the music very MUSICAL.
If I have to be honest,as a Sony’s Fanboy (golden era) I am rather sorry with the review and the opinion you had about the R10. As for me, having had the opportunity to compare the R10 to other headphones of the caliber of susvara, I noticed difference in detail, sure, but not to the point of creating a chasm. But this is an almost useless detail,as all us know that the electrostatic headphone has no rival in detail.
While where I disagree and the general review you described,(but not because I want to go against or defend necessarily my favorite headphones, it is a fact), my impressions are totally different... And like all other users I am sure that this difference could be filled by replacing properly The sponges with es labs foam.
The R10 have some of the best articulated bass I’ve ever heard,not the strongest but best articulated.
The mids as you say are the star of the show,this frequencies are seriously near the reality.
And for highs (and I suffer harsh headphone) the R10 show one of the best airy highs I’ve ever heard in a DYNAMIC headphone and in any headphones (Stax IMHO is much superior in this category),sweet and extended,and I’ve never felt any harshness or any grain of stress in my ears.
Give it another chance with the right foam
I feel the difference when I heard first times my R10 from the second time (the inner foams were destroyed after the second listening session, I guess that before being sold the headphones had not been heard after a while)
And was UNLISTENABLE.