But I was reliably informed this never happens! (Reasons I own an NEC commercial display instead)

Ah NEC. There's a name I haven't heard in a long time. I used to have an NEC monitor.

Which NEC commercial display do you have? How do you like it for normal TV duties? What tradeoffs were you willing to make when you bought it compared to the features which were available in consumer-focused "smart" TVs?

Are you confused between TVs selling your viewing habits using automated content recognition (which they all do and is well documented), vs TVs finding nefarious ways to still upload that data even after disabling network access? Because the latter is conspiracy theories and there's no evidence of it happening (and it would be trivial to verify if it was).

By who? Manufacturers have been public about selling viewing data and put it in their user agreements.