you don't have to "worry" about wifi war driving per se - you just have to know that google already does it and likely sells that information to other companies. No need to worry except to know its likely already occurring.

And in terms of legality - you likely give them permission to do whatever they want in the terms and services you agree to on first boot, or install an app on your phone, etc. And you have no control of the TV's wifi - unless you hack the encryption or get direct access to the firmware you might never be able to tell whats going on. That's definitely beyond my capabilities.

How would you spot that one? It would appear to them to be traffic coming from their TV, and you wouldn't see anything on your own net. Unless that's similar to how hotspotting works, where the TTL is different.

Also, isn't wifi sharing how many products work these days, such as various find my phone features and Amazon devices?

A simple Wifi scanner would give you a list of wifi signals around you. So, if a TV is surreptitiously creating a wifi hot spot, it would be on that list and someone would have spotted it by now... I have some digging to do this weekend.