Now this is coming from a stan's perspective... but Utada sans Hikaru is kind of a freak for her English albums, isn't she?
Songs like "Dirty Desire" with lines like During my nine to five / I'm thinkin' 6 and 9's and I don't want just a bite, I want the full size, and "The Workout" which in itself is by far one of the sexiest sounding songs from Utada; Push it up, push it down & If you want, you can come, come, get it, get it. Sure, it's only two, but they're such a departure, sonically, and somewhat lyrically from her JP work, it must've came up in someone else's mind.
Yes she is. I think the main reason is that she and her label wanted to westernize as much as possible so that means sexual lyrics, and another reason is that English is a much less poetic language than Japanese.