In Azure Sphere, Pluton didn't do any direct network communication, that was all handled by the main core. Also there was no cellular so the whole system depended on user interaction to get online.

When the main core wanted to talk to the Azure Sphere cloud service (from Linux user land), it would go through a remote attestation process that involved Pluton. Pluton can securely track what software was booted on the main core (called "measure boot") and it basically sends a hash of that to the cloud to prove to the cloud what software is currently running.

So I imagine the chip-to-cloud thing they're talking about is this remote attestation protocol.

Also, it's possible the term "Pluton" has been expanded to refer to more than just the M4 chip we used in Azure Sphere.