You're looking at v2 documentation. The current version is v3.
You can find the docs for the current version here.
Universal Routes
You may want to use some routes, such as Auth::routes(), in both your tenant app and your central app. To do this, use the universal middleware group on the route(s).
Another example of when you might want to do this is if you want to use Laravel Nova in the tenant app as well as in the central app.