I'm tempted to say that it's good enough for something where the reader won't need to do actual math with the information. He's just trying to get across the point that the drag increases faster than linearly. "Increases polynomially" would be more correct, but would get the message across to fewer readers. "Exponentially" is inaccurate, but conveys the message more accurately than any other phrasing that readily comes to mind.
And I'm tempted to say that what distinguishes math from most other forms of expression is precision, and if you're not going to be precise, you should avoid blatantly mathematical language.
