This assumes a certain (low) level of malicious intent. A fully malicious TV will connect to open WiFi nearby or use even more exotic methods to exfiltrate data.
Connect to your own wifi and block any traffic?
Even if they don't do this yet it's only a matter of time before the manufacturers catch on and start doing so.
>If you've got logic to connect to nearby open Wi-Fi, why wouldn't you also use it as a fallback if the primary Wi-Fi is down?
One idea to counter this would be to use something like this[1] to deauth the TV instantly, or spam a bunch of open networks so it gets stuck trying to connect to those rather than actually working ones.
Even if it can be blocked, I don't recommend anyone buy these and look for alternatives (commercial displays, old second-hand ones, https://ironcast.tv, etc)