Published:false for pages in /source and in /localizable

So I know I can use published: false in frontmatter inside article pages but seems like I can’t make it work in other places in source like /source/privacy.html.haml or source/localizable/custom-page.html.haml

How can I keep draft versions of these pages since published: false doesn’t’ work?

published: false is a blog-extension feature, so it can’t be applied to normal web development cycle for all pages. You just don’t publish the site until all necessary pages are ready. You don’t publish changes until new version of a page is ready. Or you make a separate fork in versioning.