The issue with the ScarJo case, irrespective of the facts behind the development of OpenAI's voices, is that a) ScarJo's team indicated an intent to sue and b) legal precedent exists that can give the performer ownership if it's uncannily similar.
It's not as clear cut as non-lawyer tech people say it is even if it will be an uphill battle for ScarJo, which is what makes it more interesting. She did fight Disney and won, after all.