It could very well be that since we're talking about a pellet travelling at 500mph in a 5mph wind, the side profile of the pellet makes an insignificant difference.
I can't ignore the fact that this wind drift calc has been used for a long long time by people who do have access to every conceivable test condition... but is there a difference between a bullet and a pellet that could invalidate the wind drift calc?.
Something that is taken as a given in the calc is that the 'bullet' will remain pointing forwards and won't have a tendency to yaw in the wind. Waisted diablo pellets from airguns don't spin nearly as fast and have a different CofG dynamic. They use the drag of the skirt to remain stable in flight - so is it possible that this has an effect on the calculation and that different pellet profiles might have less lateral yaw stability?
That would explain why those tin dynamic pellets shoot well when it's not windy and then blow all over the shop in the slightest breeze. From what I remember, they have a pretty good BC, but what they don't have is lateral flight stability perhaps?