If you have a physicist friend, ask him about 'frames of reference'.
Depending on your latitude, you have a velocity (relative to the centre of the globe you are airborne above) of between 450 and zero metres/second, plus the vector sum of your groundspeed. Now, does turning downwind at the North Pole, and doing it at the Equator have a different effect? Discuss (as my lecturer used to say).
The bright ones will catch on, the rest go by whatever book they trust.
Wind gradient is very important, (as is the optical illusion of speed over the ground), but a totally different effect from 'inertia'.