TVs have decent built-in speakers, a remote, probably more inputs, antenna/cable tuners, and a focus on large sizes, while not being so optimized for low-latency input.
> It should have exactly as much processing power as is required to pipe an hdmi signal to the panel and nothing more. [...] I'd even prefer it not have speakers.
I mean it needs a tuner to actually qualify as a TV. The bit about latencies and form factor, as well as the pricing for such, is also critical. As is the remote.
If he truly doesn’t care about any of those things, then I doubt he’d be here complaining about it. So imo at least some combination of the above is implicit.