It was posted by the tech reporter at NPR. Inb4 “journos can’t be trusted” blah blah blah, here in reality NPR is a reputable org and a reasonable person’s Bayesian priors would put this at “almost certainly an actual statement from ScarJo.”
Stuff from her comes via press agents, which is generally sent directly to reporters.
Variety has a story.[1] It doesn't yet mention an direct statement from Johannson. But watch that space. Variety is well connected in Hollywood and will check with her agent to confirm or deny.
Variety article updated: [UPDATE: Johansson released a statement saying Altman had reached out to ask her to lend her voice to ChatGPT but she declined; when she heard the demo, “I was shocked, angered and in disbelief that Mr. Altman would pursue a voice that sounded so eerily similar to mine.”]