AWS Cognito user pools

Question

I am using AWS Amplify for Flutter plugin to use Cognito for User authentication. When I executed amplify add auth followed by amplify push, a CloudFormation stack is created with several resources -including a User Pool and Identity pool.Two app clients are also created. One of them is being referred in the lib/amplifyconfiguration.dart in my Flutter App.

Using the Cognito API, I able to sign up new users to the User pool. I am able fetch Secret Keys, ID token using the following code.

CognitoAuthSession session = await Amplify.Auth.fetchAuthSession(options: CognitoSessionOptions(getAWSCredentials: true));

print('Access key: ${session.credentials.awsAccessKey}');
print('Secret Key: ${session.credentials.awsSecretKey}');
print('Identity ID:  ${session.identityId}');
print('User Pool tokens: ${session.userPoolTokens.accessToken}');
print('User Pool tokens: ${session.userPoolTokens.idToken}');

Userpool

What I don't understand is the app client that is referenced in the app did not enable the User pool as identity provider (See the picture). Also no OAuth Flow is selected.

1. My assumption is that since the Cognito User Pool is not enabled for the app client, when I tried to add a new user, the could should fail. But, it did not.
2. As no OAuth flow selected, no ID Token should be returned. But I could fetch ID Token, access token.

The Amplify cli also created an Identity pool, a couple of roles (for Unauthenticated, and authentcated users). It is referencing the User pool.

What am I missing here ? Even though the User pool is not enabled, how it is able to store users ?

Thank you for your time.