If these things include WiFi hw it's not so simple.
You'd likely be surprised what proprietary WiFi-enabled consumer products do without your knowledge. Especially in a dense residential environment, there's nothing preventing a neighbor's WiFi AP giving internet access to everything it deems eligible within range. It may be a purely behind the scenes facility, on an otherwise ostensibly secured AP.
I don't have firsthand knowledge of TVs doing this, but other consumer devices with WiFi most definitely do this. If you don't control the software driving the TV, and the TV has WiFi hardware, I would assume it's at the very least in the cards.
It's rationalized by the vendors as a service to the customer. The mobile app needs to be able to configure the device via the cloud, so increasing the ability for said device to reach cloud by whatever means necessary is a customer benefit.
It most certainly is. It's not wifi, but it's definitely a thing. It lives down in the 900MHz world where things tend to be slower, but also travel further.
And of course: If it exists, it can be used.
That said, I haven't seen any evidence that suggests that televisions and streaming boxes are using it.
I’d kinda forgotten about it until someone mentioned open WiFi, and this seems like a use case tailor made for it. If not already, it looks like a near certainty to me.
Available as a one-time extra-cost feature on the first Kindle back in '07, Whispernet provided a bit of slow Internet access over cellular networks -- without additional payments or contracts or computers.
And really, Whispernet was great in that role.
But the world of data is shaped a lot differently these days. Data is a lot more-available and much less-expensive than it was back then, ~18 years ago -- and codecs have improved by leaps-and-bounds in terms of data efficiency.
Radios are also less expensive and more-capable compared to what they were in '07.
This will be sold as a feature: "Now with Amazon Whispernet, your new Amazon Fire TV will let you stream as much ad-supported TV as you want! For free! No home Internet connection or bulky antenna required! Say no to monthly bills and wanky-janky setups, and say yes to Amazon Fire TV!"
The future will be advertising. (Always has been, but always will be, too.)
Amazon Sidewalk is more about things connecting to the neighbor's always-plugged-in Echo Dot speaker than it is about them connecting to people walking down literal sidewalks.
As a thought exercise ask yourself would you notice if any of your closed WiFi-enabled hw scanned for APs and occasionally phoned home, if it didn't go out of its way to inform you of this? What would prevent the vendor from doing so?
You'd likely be surprised what proprietary WiFi-enabled consumer products do without your knowledge. Especially in a dense residential environment, there's nothing preventing a neighbor's WiFi AP giving internet access to everything it deems eligible within range. It may be a purely behind the scenes facility, on an otherwise ostensibly secured AP.