It’s extremely clear that their intent was to use her voice, not just a gestalt or tone, given that they approached her multiple times—including after they’d actually implemented it using another voice actor.
Do you really think that everything exists in a a vacuum and must be decided from first principles, giving the maximum benefit of the doubt to one party over another? There is extensive case law on exactly this situation, and OpenAI has run afoul of it.
That person's (Scarlet) voice just happens to be a great match for the intended tone and since they refused, they went to the next candidate.