The Export step cannot set the creation date or other metadata. It is a system function, like a Save as dialog on Mac, Drafts is handing off the content to the system, and the file selection/write process is all handled out of the app’s process because of sandbox security.
If you want to update that information, you have to use the File step or a scripted action, and it has to write to the “Drafts” folder in iCloud Drive, or a bookmarked folder, so that Drafts has security permissions to access that file.
You could, in theory, write a scripted action that provided a custom file-picker, but it would be limited in scope to only one of those destinations.