Drafts uses iCloud for sync, which is not quite the same as iCloud Drive which is for file storage. No other options are available that would allow for automatic two-way sync. In system management terms, Apple groups them both under the broader ‘iCloud’ options.
Drafts’ drafts are not files. They are database records. They hold not only the content of the current version, but also past versions too, and meta data about each.
As you note, there are automations for imports of file content into to Drafts, but there is no true sync outside of the app’s database being available on all devices, and that is managed through [Cloud Kit].
Without the sync functionality that Apple provides in Cloud Kit, there is currently no automated sync for Drafts.