How does the service know who you are? That's the point of authentication. Once that question is settled, the service can decide what you are authorized to do. You need both.
Thank you for asking. It's a difficult concept to wrap one's head around, but I think the video attached to the blog post shows it most clearly. There's no authentication with the application in the traditional sense, and the application never asks for your identity. You ARE authenticated with the database provider (ayb's thedata.zone in the video), which passes a token to the application so that the app can prove it has been authorized to access the database on future requests.