Difference in documentation for Azure Push Notifications in Xamarin

Question

I am trying to understand why there are two pages that seem to document the process developing push notification capabilities in Xamarin

https://learn.microsoft.com/en-us/azure/developer/mobile-apps/notification-hubs-backend-service-xamarin-forms#configure-the-native-ios-project-for-push-notifications

https://learn.microsoft.com/en-us/azure/notification-hubs/xamarin-notification-hubs-push-notifications-android-gcm

The second link points to development for Android, with the process for iOS in the same section as well, along with the date posted being more recent. However, the first link includes interfacing with a backend service in order to register, unregister, and include tags when registering.

Could someone help explain why there are two similar yet different docs, which I should be following, and if it's the second link, how I go about registering the device with tags, interfacing with my current backend service?