What this does. Discord will ask you to approve one set of permissions, the same one the staff hub uses, so the screen also mentions your linked accounts and the servers you are in.

What an application keeps. Your username, your Discord ID, your display name and your avatar. If you are in the Beyond Sandbox server, also your nickname there and the date you joined.

Nothing is posted, nothing is sent on your behalf and this gives you no access to the staff hub.