OpenAI's mistake was caving to SJ. They should have kept Sky and told SJ to get lost. If SJ sued, they could simply prove another voice actor was used and make the legitimate argument that SJ doesn't have a monopoly on voices similar to hers.
OpenAI should’ve owned their actions. "Yes, we wanted to get a voice that sounded like the one from Her." There’s nothing wrong with that.
You can have an opinion on it, but they are going to get sued. Just like I can't take Moana and throw her in an ad where it says "I like [insert cereal here]", they can't take a character and use it without expecting Disney/whoever to come sue them.