Sky has been in the app for many months, the release last week didn't add the voice, it merely is for a mode which allows a much more natural back and forth and interaction via voice, which is, indeed, fairly reminiscent of the voice interface in "her".

He probably just really wants to actually have SJ's voice from the film. But SJ doesn't really have a right to arbitrary west coast vocal fry female voices. Without the "disembodied voice of an AI" element, I don't think most people would note "Oh she sounds like SJ". In fact, that's what the voice actress herself has said -- she hadn't gotten compared to SJ before this.