Look at it this way: when you are drifting in air, the airplane is out of contact with ground and therefore, for the constraints of movement, it is irrelevant what the underlying ground is doing.
When the airplane touches ground, anywhere, the support points affect the aircraft movement, both vertically and (unless completely freely sliding) horizontally.
I should assume that the effects of weathercocking would be rather different depending on which wheels contact ground (e. g. front wheels on ground, tailwheel off ground, vs. main wheels supported, nosewheel off ground...). Drift and sideslip should work in a more similar manner.