OpenAI first demoed and launched the “Sky” voice in November last year. The new demo doesn’t appear to have a new voice.
I doubt it would take them long to prepare a new voice, and who’s to say they wouldn’t delay the announcements for a ScarJo voice?
A charitable interpretation of the “her” tweet would be a comparison to the conversational and AI capabilities of the product, not the voice specifically, but it’s certainly not a good look.