You are angry with MacWorld because they did not give you the results you wanted. How do you know that the 1.8 wasn't running spotlight in the background and isn't even faster than the benchmark says it is?
First, I don't even own a MBA, so I don't care either way.
However, forget about comparing to previous generation. Look at the result of the 2009 1.86G vs 2.13G.
If you still think that test is valid, I can only say you have lost it.
When the test doesn't make sense, it is up to the tester to investigate and find out what's causing it. It could be anything (OS, spotlight, or maybe as you said, heat). MacWorld did not do that. That's where it is lacking comparing to the other tech sites.
So, all we have here are guesses (good or bad). That's not what a publication like MacWorld should do with their testing.