Yes, it is possible for auth0-js checkSession() to identify authentication performed through auth0-spa-js's universal login on a different page, as long as both libraries are configured to use the same Auth0 client and domain. When the user logs in with auth0-spa-js on a different page, their session information will be stored in a cookie or local storage. When checkSession() is called on the current page, it will check for this session information and use it to identify the user's authenticated state.
