> Just disconnecting from Wifi often doesn't work because the TV will connect to insecure wifi to upload data

Is there any evidence of this actually happening? It's oft stated yet I've never seen any proof or specific models where this has been observed.

It made more sense when I first heard this theorized back in the early 2010s when smart TVs were becoming more common and unsecured WiFi hadn't vanished completely yet. Now it would be way more logical to include a cheap 5g radio, which has also been alleged but I haven't seen any model shown to include one.