react-firestore-authentication | 🔥Boilerplate Project for Authentication with Firestore in React | Authentication library

Following this react-firestore-tutorial and the GitHub code. I wonder if the following is correct way to use the onAuthStateChanged or if I have understod this incorrect I'm just confused if this is the right way.

CodeSandBox fully connect with a test-account with apikey to Firebase!! so you can try it what I mean and I can learn this.

(NOTE: Firebase is blocking Codesandbox url even it's in Authorised domains, sorry about that but you can still see the code)

t {code: "auth/too-many-requests", message: "We have blocked all requests from this device due to unusual activity. Try again later.", a: null}a:

Note this is a Reactjs-Vanilla fully fledge advanced website using only;
React 16.6
React Router 5
Firebase 7

Here in the code the Firebase.js have this onAuthStateChanged and its called from two different components and also multiple times and what I understand one should only set it up once and then listen for it's callback. Calling it multiple times will that not create many listeners?

Can someone have a look at this code is this normal in Reactjs to handle onAuthStateChanged? (src\components\Firebase\firebase.js)