Why is an authentication URL not required in a different type of Oauth 2.0 provision, other than an authorization code?

Question

I have a good knowledge of all types of Oauth grants, including a precedent, but I have a question, I saw many examples of authorization codes, so if I’m talking about a partial stage of providing an authorization code type, where the client really needs to register it independently with the server resource, therefore it must provide two URLs

1.Redirect URL (where the client wants to go with his authorization code)
Authentication URL (which will come to you)

therefore, when the client makes the actual call, these things are checked, so my question is Why auth 2.0 does not recommend using the authentication URL with a different type of grant, especially I take on the client’s credentials why we cannot with it.

Answer 1

The authentication URL is the URL of the "auth server" where the "client" redirects the "user" for authentication and authorization.

Redirect Url is the URL where the "user" is redirected (along with the authorization code) to the "auth server" after successful authentication and authorization.