When you create a post in the CMS it creates a database entry. There currently isn't away to export the database so the only way to move the post would be to manually (copy and paste) move the content. Not ideal.
I think I have herd that they are looking into creating a database import feature for moving blogs to Webflow. So maybe they will also create a database export function as well.
Yeah, that's a total deal breaker for most of my clients. No way I'll be able to convince people to give up their content like that.
Hope someone fixes that soon, otherwise there really isn't a way I feel comfortable using this CMS with client data.