I share your suspicion on the "supercharged while docked" theory. I'd accept the possibility that there's a small increase in clocks while docked to allow the system to run at 720p rather than 540p, but I don't expect any more than that.
"Supercharged while docked" doesn't really mean anything, as the speculation is simply about the chip being able to run at full speed in that situation opposed to a "handheld mode" that heavily downclocks it to save battery life and avoid overheating when you play on the go.
Still, we have 4 reports:
1) Tegra X1 being noisy in devkits would point to an overclocked chip that simulates the (better) performances of the final one
2) Osirisblack saying that the console has little to no issue in handling ports from current gen
3) LCGeek's comment about NX CPU>>>>Xbone CPU
4) Emily Rogers saying that the NX blows the Wii U out of the water, and that it's close to Xbox One (although that's a bit of a stretch, but if it wasn't somewhat close then i don't even see the point in mentioning the Microsoft console, just say that it's noticeably better than the Wii U but still far from the current gen consoles)
All of these point to a console at least over 6-700gflops, while Gaf's speculation is about NX being barely above Wii U or on par/worst but with a 540p screen, which directly contradicts all of them. But those specs are impossible to achieve on a handheld, and that's why i keep saying that there must be something going on with the dock, imho it's the only way that all these reports can fit together.
It's only speculation from my part and i'm open to being wrong, but i really don't see the point in even mentioning the dock if it doesn't do anything (e.g. if it's like the 3DS one, where you simply put the console on it to charge it). It would just a portable with a TV out and a dock put in the pack for convenience.