Putting on my old 3.5 rules lawyer glasses, that seems an exceptionally strong reading of the flavor text. For example, there is nothing in the sprint section that doesn't say its an injury...maybe I pulled a hamstring or something.That's one part of the section. There's a line before and a line after that which put it into context:
"Sometimes during an encounter, a creature will gain an injury representing a serious wound. This is represented by fatigue."
"During the heat of battle it is easy to fight on without realizing the extent of your injuries."
Not the extent of your Tiredness. Not the extent of your Fatigue. The Injuries that are only being -represented- as Fatigue.
Taken in context, especially since there are 6 levels of Fatigue before Doomed on the standard track and only 4 levels of fatigue before Doomed on the Suffering track, it only applies to Suffering Fatigue. Not general fatigue, but fatigue -caused- by Suffering.
The mechanics as written right now are pretty darn clear. There is no "injury fatigue, social fatigue, tired fatigued, etc etc" there is fatigue. Fatigue gained during combat does not affect you during that combat. That's it....there is nothing else. The ONLY thing that makes sprint special is that its fatigue ends more quickly, and that is specifically noted. You cannot push that phrasing to mean any more than what it says it means....it does not create some special category for sprint that makes it immune to all the other rules of fatigue.
And just for one more log on the fire....if we do want to go down the flavor text debate you noted at the beginning....than does it really make sense that I can ignore the effects of a heinous injury, an injury bad enough that it requires 5th level healing magic to undo, but I can't ignore the effect of getting a bit winded after a 6 second run?