If you're worried about privacy just don't connect it to the Internet and buy a smart TV stick of your choice instead that you plug into the HDMI port of the TV (or use a Raspberry Pi if you don't trust those either). Problem solved.
Probably 99 % of people are fine with owning a smart TV, so it's clear that manufacturers won't cater to the 1 % that are not fine with it.
There are more legitimate reasons. If you are one of the few people who live in a radio quiet zone, or if you suspect 2.4GHz interference with other 2.4GHz radios you use, or if you develop and test RF gear, you'd want to be able to disable the radio.
Pretty sure you’re being sarcastic saying that’s a valid thing to expect end users to do to opt out. And I agree. Wish mining peoples privacy wasn’t accepted norm.
Smart TVs are relatively cheap compared to large industrial displays. They are also reliable. If you need large secure (no wifi) display, this is pefectly valid option.
There's a thread on Reddit [1] but the poster never replied when people asked about the exact model and no one else reported this behavior, so I'm skeptical (I own a Samsung smart TV and from my experience it always asks you before attempting to connect to any wifi network). From the manufacturers' point of view it wouldn't make much sense auto-connecting to an arbitrary open network as that will in many cases just lead to an unusable connection, so I have a hard time believing Samsung would actually do this. What's more likely is that someone else (spouse, kid) used the TV, selected an open wifi and the TV saved that without OP knowing. But who knows, maybe Samsung is really after us.
Anyway, if you're so worried about the device maker spying on you it's probably best to avoid buying such a device (or any kind of smart device including a smartphone). In that case just use a monitor instead.
Probably 99 % of people are fine with owning a smart TV, so it's clear that manufacturers won't cater to the 1 % that are not fine with it.