I don't get why JVC is following Sony down a dead end with true 4K.
4096 x 2160 will deliver an inferior image to 3840 x 2160 in ALL usage scenarios other than with DCI content which cannot be purchased by consumers.
Facts: With UHD Bluray content or streaming UHD content, 99.9999% of which is in 16:9 aspect ratio (3840x2160 or 1920x1080), you should watch it in pillarbox to avoid unnecessary re-scaling which costs sharpness. That's entire point of high res, which is defeated by extra rescaling / resampling steps. This is 100% incontrovertible. Don't do it. Either with UHD or FHD content, stick to 1:1 aspect ratio upscaling for FHD and avoid any scaling whatsoever for UHD content.
Given that true 4K content is basically nil, why the extra 6% of pixels?
Q) Will it cost me anything to just leave those blank? YES : LUMENS. Lumens matter for HDR, and 3D, and even 2D.
Imagine losing 6% of your brightness to project black pillars 100% of the time. This is dumb and wasteful. Do people even sell 17:9 aspect ratio screens? Probably cost way more if they do even exist.
From what I can tell, there is no technical upside to using a non-standard resolution (or at least non-standard in the consumer market). Unless you can buy 4096x2160p content, that is, but UHD Bluray is fixed at 3840x2160 and that respresents the highest you can get for consumers. Meaning, this extra resolution is a strict negative, in the sense that you are losing lumens for nothing but paying more for the privilege.
The real reason for true 4K, I believe, is simply a checkbox for bragging rights, and serving the same market of individuals who "need" speaker cables that cost thousands.
This has been a minority report and a public service, thank you for listening. JVC, don't give us useless features, give us 120hz input support at 1080p with HDR and low latency and you will be loved long-time. But no, instead, we get 17:9 aspect ratio chips, 6% of which will never be used except for anamorphic lens users, and even then, at 4K many lenses are not sharp enough to deliver a sharp image, plus 1.25X lenses cost way more than 1.33X lenses and are rarer and harder to find.
And even worse, using a 1.25X lens requires your anamorphic stretch to scale letterbox content both vertically (1600 -> 2160) and horizontally (3840 -> 4096). More scaling is worse than less scaling. This is also a fact.
4096 x 2160p : All kinds of wrong for consumers. But yay, let's offer people useless stuff, it looks great on paper! They probably won't even notice or care that 6% of their lumens are never going to be used.