Yes it's true that people are rightly doubting the methodology.
However if the data showed the exact opposite result (Google having better results than Bing) I think the reaction on HN would be to accept the results at face value. This despite the fact that there is no reason (that I'm aware of) that Google search results should be inherently better than Bing.
In this instance, I think it shows the strength of the Google brand and how the strength of that brand sets users expectations for the quality of the results.
However if the data showed the exact opposite result (Google having better results than Bing) I think the reaction on HN would be to accept the results at face value. This despite the fact that there is no reason (that I'm aware of) that Google search results should be inherently better than Bing.
In this instance, I think it shows the strength of the Google brand and how the strength of that brand sets users expectations for the quality of the results.