So you are knowingly helping Samsung spy on your neighbor. Have you thought about the ethics of what you are doing.

Anyway while I would not call the original accusation of the TV using any open WIFI automatically out of the question this experiment provides little evidence of that. It's hardly unthinkable that your neighbor or someone using their TV just clicked OK on some prompts to make them go away and thereby selecting the first network in the list. It's also not unthinkable that your neighbor wanted to use some functionality that requires an internet connection to setup and just didn't pay attention to the WIFI network selection.