When using Deferred Activation, the operating system will be in "Notification mode", which means that it will remind the user to activate the operating system every time the user logs in. However, the operating system will still be fully functional and can be used as normal
command "slmgr /xpr" and it should show that the Windows is in Notification mode.
If you are seeing the message "Unable to reach Windows activation servers" after final installation, it means that the device is unable to connect to the internet. This message is expected, as the device does not have internet access and the activation servers cannot be reached. The operating system should still be in Notification mode, and the user should be able to activate it later when internet connection is available.
So, yes, the state of "Windows is in Notification mode" is the correct deferred activation state when the internet connection is not available during the final installation, and it will remind the user to activate the operating system every time the user logs in.