But in the real world it is common to need information from the authorization stage to use in the authentication stage. For example you may have a user login with an email address/password which you then pass to an LDAP server in order to get a userId. This userId is then used in a database to determine with objects/groups they have access to.
A lower latency design would be for the authorization service to be able to work with either. That way those requests could be done in parallel to reduce latency.