But they asked her first!:
"Last September, I received an offer from Sam Altman, who wanted to hire me to voice the current ChatGPT 4.0 system. He told me that he felt that by my voicing the system, I could bridge the gap between tech companies and creatives and help consumers to feel comfortable with the seismic shift concerning humans and Al. He said he felt that my voice would be comforting to people....
https://twitter.com/BobbyAllyn/status/1792679435701014908
So its: ask Johansson, get declined, ask casting directors for the type of voice actors they are interested in, listened to 400 voices, choose one that sounds like the actor, ask Johansson again, get declined again, publish with a reference to Johansson film, claim the voice has nothing todo with Johansson.
[EDIT] Actually it looks like they selected the Sky actor before they asked Johansson and claim that she would have been the 6th voice, its still hard to believe they didn't intend it to sound like the voice in her though:
https://openai.com/index/how-the-voices-for-chatgpt-were-cho...