Altman tweeted a reference to Her. (Literally just that text.)
The assertion that this one tweet, in the absence of any other official communication, constitutes advertising the product to be voiced by Scarlett Johansson is a _huge_ stretch.
I'm certain OpenAI would have been much happier with SJ as the voice actress. But how different does a female voice have to be to _not_ be considered an impersonation of someone?
I think the fact that the AI in the OpenAI demos acts like it is at a similar level to Her is far more impressive than the voice may sound like the one SJ did for that movie. Impressively mimicked voices aren't that new. Amazon sold a Samuel L Jackson Alexa voice years ago.