Why or how is this superior to working with a word document?
Authorea has its own version control system. So if you have altered file contents and wanted to revert to a previous saved version, it’d be possible to do so. Besides, this would allow dynamic updating of the file by tens of contributors at the same time. Unlike working with Word where we send files back and forth, we work here from a single file and all changes are reflected as we work on them. This is similar to what happens in Google Docs but with the difference that you can add footnotes or citations if you want or additional annotations and repeatedly upload and download it.
If you do not want to repeatedly upload and download files, you can set up a git connection to the file and work from there. Click on the “wheel” at the corner of the article, and set up a git repo for this article depending on your preferred git repository (github/gitlab/bitbucket). Then push and pull through the git if you want to. This is what I do for my article writing, so I have to barely touch Authorea after I have created an article or book chapter once.