I am a bit confused about the Moodle office integrations.
I thought that, at its simplest, the concept was, for example: You have, for example, a Word document in your OneDrive or Google drive or Drop box, that you want to submit as your Assignment. Instead of downloading the file to your desktop, then reuploading it, if you Moodle site admin has set up the right plugins, you can just select the file directly in the file-picker (after logging in to the other system.)
What acutally seems to happen is that, for example, a student can only pick a file from OneDrive if it is an institutional onedrive that you are providing to students. If the student is already using a personal onedrive account, they are out of luck.
Have I got that right? It seems a bit disappointing if so.