That's the point though. TVs like from TFA are preventing use when air gapped. As more manufacturers go this route, there will be fewer tvs that will allow that to work

Are they?

I skimmed TFA and what I consider "Smart TV features" are the things the Shield does: Apps, streaming, etc.

I see no indication that picture settings or HDMI features are disabled without an account.

I have a Samsung TV that is "smart" but I use a Shield and never touch my TV remote unless I need to adjust a picture setting.