It's exactly the same thing, which is why it's bad. When I log into e.g. CoolQuiz[0] on quizzes.cambridgeanalytica.com with Facebook using OAuth 2, it requests

It's exactly the same thing, which is why it's bad. When I log into e.g. CoolQuiz[0] on quizzes.cambridgeanalytica.com with Facebook using OAuth 2, it requests a limited list of permissions from Facebook, which are shown to a user, and which don't include things like like resetting the user's password or changing the user's email address. It gets back an access token which can only be used for doing those things, and Facebook can track what's done with that access token, in the case that e.g. CoolQuiz uses it to read personal information from all a user's friends and microtarget advertising during a US election. Headless chrome is indistinguishable from a normal user, which means it can do absolutely anything a user can do and can't be tracked. [0] probably doesn't exist, just a hypothetical example