There is a complex design question here, and we have an interesting example of a platform holder blowing it.
Nintendo obviously wants a system that looks good on modern 4K TVs. But their launch Switch game ran at 900p. 4K is 6 times as many pixels. That’s a whole generational upgrade spent just on uprezzing.
Nintendo will support full 4K output. But while designing the console, I think the software devs are going to look at how much power the hardware folks have to offer and settle on 1440p as the default “next gen” target. It still looks good on modern screens, and it leaves plenty of room to make all those pixels look good, too.
1440p means instead of a 4x gap, we can do a 2x gap with handheld. Which is much easier to manage than 4x. Because you don’t want to just throw power at the problem, ideally you want to match the two. The best possible handheld mode + best possible docked mode doesn’t equal the best system.
Which brings us to the platform holder who screwed all this up, Microsoft.
The Series X is the most powerful console on the market. The S, which loses Microsoft twice as much money per unit, really probably is the most powerful device that MS could offer at an entry-level price point. They smartly target 4K and 1440p, respectively.
So why do they suck so bad?
Well, lots of reasons, but at least part if it is because the two consoles don't support each other. The S is supposed to hit half the resolution of the X, but only has a third of the power. The S has too little RAM, and terrible memory bandwidth, leaving the two machines to require different sets of optimizations. The S's RT performance is so poor that what should be the generation's defining innovation is often turned off. Meanwhile, the X's extra power is mostly wasted, with exclusives needing to scale down to the S, and mulitplats getting "good enough" at the PS5's level of performance.
Nintendo wants to dodge all these mistakes. That means, ideally, matching performance to the target resolutions, so that, as much as possible it’s one port not two. That also means avoiding things like one mode having drastically different bandwidth capabilities.
Which brings me to T239 itself. It’s worth remembering that T239 is fully custom, not off the shelf. So if there are limitations, they’re either baked into the tech, or something Nintendo actively chose. I would be wary of any thinking that only works if T239 is pushed past the design’s natural limits.