The intel/amd parts look massive compared to anything ARM I've seen lately. Maybe the CPU's comparable to an old QFP ARM2/3 in a socket, but those weren't also burdened with a hot GPU. Modern ARM chips come with the GPU in-die and the overall form factor is about thumbnail sized or smaller as far as I've seen.
I wouldn't put it past many of ptitseb's ports in particular to stress that CPU+GPU combo in a particular performant way for almost as long as you're playing them. We may need to reduce settings to enable longer spans of gameplay that don't stutter.
Well yeah, this isn't quite something where it's the size of your thumbnail. This sort of thing is generally more intended for something laptop or home media PC-sized.
That said, that's not to say it can't fit in something more portable. And while it's not all in a single die, it is a CPU + GPU + (in this case) HBM2 solution. You'd still need RAM and the general purpose components and the like, but while it's physically bigger, it still is the "essential" piece of the computer all in one, and it's not much bigger than a normal desktop or laptop CPU die from the looks of it (based on the images Intel put out, anyway). That's still something you could fit into a portable device.
It could be fit into something still portable, but the main issue would still be physical size of the device as well as heat generation/dissipation. The main thing I was getting at was that with a lot of people carrying bags to/from work, the idea that it has to strictly be pocket-sized isn't one that might need to be adhered to like law. Again, the Switch is definitely NOT pocket-sized - 6.2 inches diagonal is a fair bit bigger than most phones (which top out around 5.5 inches), and that's without the Joy-Cons being attached, which easily add another 1-1 1/2 inches.
The thought of a bigger device (Pyra XC - for "Xtra Crispy") does solve some of the issues people would have with the Pyra/Pandora, namely that it doesn't have the oomph of some of the more medium-sized portables around, while at the same time, still being small enough to be actually portable. We can tout the portableness and the respectable power of the ARM chips all we want - they're still a very niche product, compared to something like the GPD Win which set the world on fire... until it crashed and burned, precisely because it could run Windows and thus all the normal sorts of stuff that people want to play on that. Pyra is a niche device - making it mainstream definitely means moving in an x86 direction and away from ARM, as while they're certainly more power-efficient, at best all they'll match is a smartphone, and most people already have one of those.
The main issues would be, again, what kind of heating/cooling system it can employ, battery life, and so on. And, of course, the fact it DOES need to be portable (and to have ED able to buy the components in batches, which is why nVidia turned him down on trying to get Tegra stuff, which sucks for us but we take what we can get.)
Personally I know I keep envying those Portable Playstation 2s some hobbyists are able to build - but am also horrified that it takes literally gutting and sawing a PS2 in order to make it happen. Even a modest CPU like that should be able to run PCSX2 at a decent framerate, but an ARM chip doesn't have a prayer of it - it's simply not got the mustard.