Earlier quoted context omitted.
This. Why would you even connect TV to the network? It is well known for like 5 years. Smsrt TVs go through your movies library, and upload screenshots and filenames to internet. Some will start showing ads after firmware upgrade.
Watch the video the article is based on - not connecting to the internet doesn't keep you safe in many cases: https://www.youtube.com/watch?v=6IFVTcM28KA
They can just start a capture, record to RAM / storage, and retrieve it later when it is reconnected to the network.
Otherwise if it's disconnected, it is still hard to exfiltrate the data somewhere. Maybe they could get creative via Bluetooth, but then you would need a cooperating device in proximity of the device.