It is quite possible that OpenAI has synthesized the voice from SJ material.
However If OpenAI can produce the woman who did is the current voice, and she has a voice nearly identical that of SJ would that mean OpenAI had done something wrong?
Does SJ since she is a celebrity hold a "patent" right to sound like her.
The more likely scenario is that they have hired a person and told her to try and imitate how SJ sounds.
What is the law on something like that?