That's comparing some pretty average / poor / budget boards it looks like to me, so I don't think that's a good or fair example.
Do you see any with Gigabyte P67 vs Gigabyte Z68 showing that, I doubt you'll find any not because no one compared, but because it's not true?
And, even in the results you linked, those are 3-5 points apart, many even less than that, so no way that can be used as a good example because they are too close to be able to say if that's not just general differences between the times the benchmarks where ran, or minor differences in BIOSes, ect