Normally all the commands that we execute in Siri are processed in the servers of Apple. This means that anything we ask Siri will send the data to the servers to return a response. Consequently, an Internet connection is required.
However, it seems that Apple wants to change this, at least for the most basic processes. As some Reddit users have discovered, in beta 3 of iOS 11.2 Siri is able to understand some commands without having to send them to servers.
Basics such as playing music, pausing or things like that, you can do without the device is connected to the Internet.
At the moment the commands are very basic, and it seems to be related to options that can be easily executed from the AirPods. That is, if we tell him to play music he will do it, but as we ask him to play a specific album … he will ask for Internet access.
At the moment it seems to be something that only works in the beta 3 of iOS 11.2 It remains to be seen if Apple finally decides to implement it in the final version of iOS 11.2 or not.
Regardless of this, the voice commands prior to iOS did exactly the same and without an Internet connection, so there is no reason not to implement it again.