I'm not sure how much weight to give the "uncanny valley". When that term was being bantered around, people were mainly talking about CGI. We're good at detecting what's
wrong (for example, dead eyes in "The Polar Express").
It turned out that a lot of it had to do with poor animation, and I think that's the case here as well.

I give the concept weight here because it makes sense and its apparent effect on me really can be really strong.
Remember Macintalk, the "drunken Scandinavian in an oil drum"? He didn't provoke any sort of emotional response, other than yucks. He was a funny robot voice.
Likewise, I think, for decades of synthesized speech.
But now, robot voices have gotten to the point where they're beginning to enter the Zone of Indistinguishability, and they can sound
almost but not quite like humans, and for me, that's where spooky, quasi-emotional phenomena start intruding.
Maybe it's like flying a supersonic plane (he wrote, as if he knows what flying a supersonic plane is like.) As you approach the Speed of Sound, vibration and turbulence increase until
pow you pass through Mach 1 and things calm down.
You and Eleanor are Pushing the Envelope. Buckle up!