I don't think that follows. It's entirely possible that OpenAI wanted to get ScarJo, but believed that simply wasn't possible so went with a second choice. Later they decided they might as well try anyway.
This scenario does not seem implausible in the least.
Remember, Sam Altman has stated that "Her" is his favorite movie. It's inconceivable that he never considered marketing his very similar product using the film's IP.