PS4/Xbox are basically a PC in some senses yea, but they have their own mainboard layout and components. There is also a probability that X1 can run full Desktop, I don't know if anyone has tried though. I read an article a while back stating it's original OS is almost indistinguishable from Windows 8.1 on Desktop PCs.
The difference here is that Shield TV, Switch, and Jetson TX1 are all essentially the same board. That is different than containing similar components to another platform, they are the same components. I can't say for the Shield itself, but if I remember right, Nintendo pretty much went with a mostly unmodified jetson kit. I could be remembering wrong though. So far all the Jetson information I have used has been helpful anyway. The Jetson TX1 also has 4GB of ram.
I don't know if I would really bother though. Also, 1GB of RAM being missing will not make that much difference if proper memory management is implemented with swap. After all, you'd be running the CFW on an alternative device so you could do some more hacky stuff. Wouldn't be worth the time though that would probably need invested. It's likely better to port everything to Switch since the other OSs (such as Android) have open source kernels and dev kits. Even the Shield has open source stuff.