I don’t know if there are any others that do, but even Brave Writer doesn’t really teach it. They mostly let it happen more than other curricula. You can totally do that without lesson plans! Freewriting is one things that’s good for that, where you don’t care what they say or correct anything about what they do write. Besides encouraging them to say what they want and sound like themselves, I like to do freewriting with them (and any other kind of writing for that matter) and let them see that it sounds like me. Then I like to tell them what I like about what they wrote and point out how it sounds like them. I think their voice comes through when they don’t have to fit some kind of formula in their writing. They can learn forms after getting really comfortable with their own voice. But I’m pretty sure most curricula don’t talk about it.