That's not oauth, that's just the granularity the auth provider has decided to expose in its permissions system, and the granularity Dropbox have opted to request.

That's oauth in the sense that if you login with your own login/pass, this will never be something they can force on you. I never use oauth, always login/pass, and don't have to care about what permissions they ask me, it's easy, they have absolutely zero access to my gmail/facebook/twitter whatever.