Not sure what you are saying here. Are you criticizing the fact that the 48% positive rate does not equal 50%, or that the fact that 48% of the tests are positive does not mean 48% of the people are positive?
While the statement may not be technically accurate to a degree sufficient for the anal-retentive, presuming Iowa has a high rate of testing, the number is reasonably accurate, and obviously the point is even more important: that rate is ENORMOUS. Whether it be 1 in 2 or 1 in 3, lots of people likely have it (unless they are only testing the symptomatic, etc. )