Which methods of Google OAuth2 API accept login_hint as a parameter

I am using the Google Sign-In JavaScript client and also referencing the Example App

The example app (app.js) tells me that login_hint is a valid option for the signIn method:

    // If the user is not signed in with expected account, let sign in.
return auth2.signIn({
  // Set `login_hint` to specify an intended user account,
  // otherwise user selection dialog will popup.
  login_hint: id || ''
});

But the reference manual does not say it does anything there but is only effective with the authorize() method. Elsewhere on the Web I see examples of it being also used with the init() method.

Can someone please clarify any/all places where the login_hint option is functionally active?

from Which methods of Google OAuth2 API accept login_hint as a parameter