The docx export is the same as the one offered in OO3 Pro for Mac. It only exports the outline column and is formatting to work with Word's outline view. If you switch to the outline view in Word, you will see your hierarchy. Styling will carry over as well, and if level styles are used, they will be created as a style in Word as well. The goal of this export option is to provide an easy way to go from the outlining phase to the full on writing that you would want to use a word processor for. It is not intended to provide a multi-column replica of your outline. Word is not really suited for that, the only way to provide actual columns in Word is with a table. Would a proper Excel export option better suit your needs?
You can download
OO3 Pro and use it in trial mode to see how the export works if you have a Mac to use.