I am trying to get this working but cannot. Here are the steps I took in case I have missed something out:

1. Set up Google as authentication method
2. Connect a system account and set up Google drive repository with Internal and External as supported files
3. Student logs in via their Google account and uploads a Google doc as an assignment using the controlled access link option
4. Teacher clicks on the link and is prompted to log into their own Google account (I tried both with an admin role and as a teacher with editothersubmission allowed)
5. They can view the document but cannot edit it unless they request access (or unless the teacher uses the site-connected Google account)