Actually it only says they reviewed "brief recordings of her initial voice test", which I assume refers to the voice test she did for OpenAI.
The "impersonating SJ" thing seems a straw man someone made up. The OpenAI talent call was for "warm, engaging, charismatic" voices sounding like 25-45 yr old (I assume SJ would have qualified, given that Altman specifically wanted her). They reviewed 400 applicants meeting this filtering criteria, and it seems threw away 395 of the ones that didn't remind Altman of SJ. It's a bit like natural selection and survival of the fittest. Take 400 giraffes, kill the 395 shortest ones, and the rest will all be tall. Go figure.