it's not just your wifi you have to worry about. neighbour can have insecure wifi. or deliberately open ones like coffee shops, free municipal hotspots, etc.
This is trivial to test yet not a single person claiming TVs will connect to open networks all on their own has ever provided a shred of evidence of it actually happening.
That sounds like a TV manufacturer is going to be having one hell of a lawsuit if they're breaking into other peoples wifi networks.
Wasn't this exactly what happened in the LG exposé that just came out? It connects to any WiFi network it can, your will be damned.