As I understand it, all brewing methods are subject to both oxidation and degradation of yummy acids and oils. I was first introduced to the 10-second rule for espresso as a customer at a Starbucks. According to the barista, if the coffee did not touch something (water, milk, syrup) within 10 seconds it would turn bitter and "burnt" tasting. I was highly skeptical of this claim, so the barista felt obliged to prove her point (which is easily testable, if you can stomach wasting a shot). She pulled a shot and immediately dropped in a teaspoon of cold water (so that I could drink it right away), then handed me the shot glass to try. Delicious. Then, she pulled another shot, we counted to 10 together, she added a teaspoon of cold water, and I drank. Bitter and burnt tasting. Not terrible, but nowhere near as complex and tasty as the first shot. The difference was marked. (Incidentally, she claimed that the temperature of the added water was irrelevant to stemming the bittering process.)
I have since tested this at home on my machine, with the same results. (And I've tested adding hot or cold water, both do seem to stem the degradation process, as she claimed.) If you are skeptical -- as you always should be -- test it (at least somewhat systematically) yourself.
Here is a site with more information about oxidation and degradation of acids and such:
I suspect that an email to the author could easily shed more light on the how and the why.