I keept the grass short so I have never noticed this so far, however it does make perfect sense.
I would suggest just changing the grass material to offset the blades vertically based on an input from the instance.
you should be able to use the Object Rotation for this.
The math should be as straightforward as counter rotating on the vertex normal by the same amount of rotation? Something to that effect.
Doing it this way should be better if you can keep the mesh base alignment (ei: use the vertex paint for the wind as a filter for the shift).
this way the mesh can be tilted to follow the landscape, but grow vertically from where each blade is placed…