There isn’t any evidence that they used her voice

There's ample evidence, via the samples OpenAI released during their demo.

Actually, there is evidence that they paid a voice actress to model that specific actress’s voice.

Actually, there's not. OpenAI refuses to release where they got their voice samples. They insist it came from "another unnamed actress".

She’s not the only person with those vocal qualities.

If the raw data OpenAI used to train its AI came from voice samples produced by Scarlett Johansson, then there actually IS only one person with those vocal qualities.

If I wanted James Earl Jones to read my eulogy, but he isn’t available or is unwilling. Why couldn’t I get someone to sound like him to read it?

Nothing is stopping you from doing this.

However, if you took an existing privately licensed James Earl Jones eulogy and doctored it with AI trained data to replace another person's name with your name, then you'd be robbing Jones of his work product.

Waving your hands and saying "But maybe I didn't do the thing I did, so actually its fine" isn't a credible defense.