Yes that's true, the problem is that some smart TVs don't work at all or only partially if not connected... and it's not easy to know which model will suffer from this, since "works without wifi" is not a commonly advertised feature, unfortunately.

I have a Ryzen-based HTPC connected to an old "dumb" TV, when that one dies, I will have to either find a store where they let me test the TV in the showroom (so I can verify that that model works with wifi turned off), or I will have to spend more and get a large monitor instead.

Alternatively I could look at "digital signage" or "hospitality" TVs which are dumb by design. However those are not easy to come by in my local market (Sydney, Australia).