Ok so I had done more listening and as promised am updating. I stand by my impressions but it's mainly due to semantics. You almost had me, almost lol.
You seem to be intertwining vocal timbre and accuracy into one wholistic definition, whereas I separate them. I maintain that vocal timbre is great because voices sound like voices. They don't sound "off" as in odd or strange or unrealistic. They have good texture, body, and weight, and don't sound hollow, stuffy, or nasal, and so on. I never mentioned vocal accuracy in my write-up and didn't imply that they had it as far as I can see. But then you can get into accuracy to what, life or recordings or masterings? And since they vary across any album, it can get dicey, no? The sibilance does hurt timbre when it shows up but it hasn't been very common in my library.
Well then I will defer to your assessment lol.
I actually think I might know where you're coming from here and in my mind has something to do with when I wrote that they sounded warm but not really inviting.