EXPO: Facebook login in different ways

I’m trying to create a simple expo app with facebook login. For this reason, as suggested by Expo, I followed this guide:

https://docs.expo.dev/guides/authentication/#facebook

Currently all works fine, I can sign in via Facebook and I did also a fetch to get the access token:

fetch(`https://graph.facebook.com/oauth/access_token?client_id=${this._authConfig.clientId}&client_secret=${this._authConfig.client_secret}&grant_type=client_credentials`);

After the access token, I thought I could retrieve my facebook data via

fetch(`https://graph.facebook.com/me?access_token=${this._getAccessToken()}`);

But the access token I retrieve from the first fetch seems to be incorrect.

An active access token must be used to query information about the current user.

I saw that people are using Facebook SDK instead this login (https://docs.expo.dev/versions/v45.0.0/sdk/facebook/), but I’m wondering why. What are the main differences between the those two guides?