Comment by hackerlight

This could be confirmation bias.

Here's an alternative explanation that fits the same facts. Sam tweeted "her", not due to the voice, but due the existence of a conversational system that resembled the system in the movie. This primed people to hear Scarlett Johansson's voice in a generically cheerful female voice actor who was contracted over half a year ago. Scarlett's lawyers encourage her to write a public letter, helping Scarlett with the wording, in order to steer the public narrative, in order to place pressure on OpenAI to settle with her financially out of court.