You're looking for "if(IE)" stuff, that's not what I meant. HMTL5 is very large. Very, very, very large. If Microsoft spends some time over-optimizing a very little subset of it on their stuff, a small subset no one else concentrates on, and then writes test case for that, of course they are going to come out on top.
There are plenty of ways vendors can write biased benchmarks. Not all of these require "trickery". Then you get users saying "WP7 destroys in HHTML5 benchmarks!" when the truth is "WP7 destroyed in tests made to show only the good sides of the HTML5 implementation on WP7 while ignoring other test cases where the competition scores better!".