Thanks for the examples! This is literally just “large vs small viewport”, though. A TV might be huge, but with a similarly large viewing distance, may actually present a much smaller viewport (in CSS px, which are technically an angular measure) than a monitor. No additional MQ is needed here; you’d present similar UI to a tablet user.
(Now, TVs might not present an appropriately-sized viewport, but that’s just a bug in their browser implementations. We don’t add features just to work around bugs; it’s simpler for everyone if the bug is just fixed.)
A trackpad is indeed a “fine” pointer; what difference in “refined experience” does this present? The coarse-pointer TV would just get larger buttons. If you’re basing a bunch of unrelated UI decisions off of pointer:fine/coarse, you’re doing it wrong and will be giving people bad experiences.
The software is irrelevant. My point is that the correct display for a TV is entirely dependent on use. You seem to understand this, but are dismissing it somehow as a software difference, rather than as a usage difference. If I run my desktop browser on my TV (and set things up so that it has a proper viewport size, etc), I should be getting the same experiences as a “TV browser” or “game console browser”. There’s no difference in environment.
Again, this is just a matter of viewport size. You don’t actually care about how far away the person is, you care about how large the screen is in their field of view, which, when set up appropriately, is automatically handled by scaling the px unit appropriately and sizing the viewport accordingly. Based on a rough eyeballing from my couch, my TV’s viewport should be about 1000px wide; that’ll give a px size similar to my laptop.
As I’ve said before, there might be more context that could be usefully provided. For example, you mention “share with others” - if this is a useful bit of information that authors would cause authors to change their page style, we can think about adding it as media query.