Look closelier. It's "semi-custom".
They clarified, the silicon is off-the-shelf and the firmware is modified. It doesn't have some "special processor" or anything.
It has everything to do with heat and noise.
What? It being small only means the heat has less room to be removed, so it needs a higher power fan (or thermal throttling). It does have something to do with heat and noise, in that smaller is worse for them. If it's quite or cool, that's despite the size, not because of it.
I don't care to argue about this, but you're making unfounded claims that this device is somehow special, because it's made by Valve I guess, and they need to be worshiped? It seems like a nice kit, but it isn't particularly groundbreaking. It's just a well designed and put together computer. Most of what it does is the same as any other computer, running Linux/Arch is capable of.