Descript saves documents as Packages, which is standard practice for Mac applications. A Package is similar to a Folder, because it contains multiple files, but these files are highly technical and are used by the software to function.
That’s why Mac OS displays a Package as a single file. There's no reason you should need to worry about how the software handles constituent parts of your project — you just care about your project. Packages make things a lot simpler.
Some file syncing services like Dropbox have issues with Packages, but as of Box Sync 4.0 (released in 2015), Box handles them properly.
This means you should be able to sync Descript projects using Box without issue, provided you use good sync hygiene. To that end:
‣ Never edit the same project simultaneously from multiple computers.
‣ Whenever you edit a file, make sure it finishes uploading before attempting to download it elsewhere. And when you go to open the file from a different machine, ensure that the file finishes downloading before attempting to open it.
If, for some reason, you find that your Box files are messed up, you may be able to restore them to a previous version. You can learn more on Box's support page.
If you're using a different file sync provider, like Dropbox, read this page.