Are you blind? They showed that there's almost no difference between DX9 VERY HIGH and DX10 VERY HIGH.
There's a HUGE difference betweeen "high" and "very high" simply because one uses parallax occlusion mapping and one doesn't. That alone makes all rocks, sticks, leaves, waves, etc. stick out more realistically therefore adding a TON of detail to everything. (also bringing frame rates way down in the process) If you use those settings in DX9 you'll get better performance than in DX10, but you're a little confused it seems, since you didn't realize what they were comparing...despite the huge writing under the images...
Try looking at screenshots of the game at more than 320x240 and compare one image on "high" with the same image on "very high" with god rays, parallax occlusion mapping, improved post-effects and object motion blur. You'll see the difference.
Exactly.