> The Matter devices (a smart bulb or a sensor) have no Internet access required by the spec, and no way to send telemetry to the Internet.

That's a little disingenuous... All Matter-over-WiFi devices inherently have Internet access unless you're blocking it through router policy, and most Matter-over-Thread border routers commercially available today give Thread devices Internet access by default if they want it (to avoid this you need to self-host your own OTBR instance).