That's interesting (and scary)! The study I read said that 90something% of hospitalized cases had fevers and that 30% or more of non-hospitalized cases did not. Perhaps some of the hospitalized cases could have developed fever later in their illness, therefore they were included in the fever group?
I was told by my kids' pediatrician that the study with the 90% was well publicized, which led to the misunderstanding that swine flu HAS to have a fever. Doctors saw the 90% and assumed that all patients would have fevers when, in fact, the study was of hospitalized cases and not others. It has taken a while for that confusion to subside, and as we have seen in posts here, not all doctors have come to the realization that you don't have to have a fever to have swine flu.