The maths can't be wrong but the model can be, and probably is.
Progress comes from challenging the status quo.
I'm unhappy with the notion that the broadside profile of the pellet has nothing to do with its wind drift, and drift only follows from the forward direction drag factor. In my day in class, force = mass times acceleration, and work done = force times distance moved. I can hear my physics master's voice today chanting the mantra, and the last time I saw him was 1961. If the pellet was frozen in time, and just hung there in mid flight, the wind would apply a force related to the dynamic pressure and the angle of incidence of the wind, and the projected area of the profile. That force, however tiny, doesn't go away just because the pellet is moving. But that isn't included in the modelling.