The Tegra X1 does 500GFlops FP32 at 11W TDP. At 22W TDP, you can double the Maxwell cores and get ~1TFlop FP32. XB1 runs 1.3TFlops.
What this means in simpler terms is that the Eurogamer article hinges entirely on the number of cores/SMs, which it doesn't reveal. Assuming 3 SMs, the math works out to Switch pushing a max of 567GFlops while docked. OTOH it could just as easily have 6, which would double that to 1.1TFlops, and that's precisely in line with what we've been led to believe is Switch's performance ballpark. AKA just a little weaker than XB1.
Crucial details are still yet to be revealed, so don't act like this is set in stone either way, and definitely don't panic yet.
Discussion started at here by Archlicht