somebodyspecial :
It has a 5.7in screen with lower res at 1080p, vs. shield at 8in 1920x1200. Last time I checked 5.3hrs is 35% longer life than 3.9hrs not 10% you claimed,
Did you actually read the graphs or did you blindly pick up the best-looking bar with Nvidia next to it and assume it was the K1?
The NVIDIA Shield (notice the missing "Tab" - that would be last year's Tegra 4 handheld) scored 5.3h but the Shield Tab scored 4.3h with GFXBench locked at 30fps. 4.3h is ~10% more than 3.9h.
If the K1 had not been capped to 30fps because "most games shouldn't come close to stressing the Kepler GPU," the K1's battery score would have been even worse: if you look dead last on the graph, without the 30fps cap, the Tegra Tab sinks to only 2.2h.
As for the resolution difference, 1920x1080 vs 1920x1200... not a big deal.
Bottom line: using K1's full power nukes batteries like nobody's business... the SoC uses close to 10W under full load.