i guess you are referring to the "AfsGrassShader". but which script do you mean? the "CombineChildren" script? you do not need the "CombineChildren" script in case you use gpu instancer – however even if it is applied gpu instancer should work properly. you do have to have an instance of the afs setup script in your scene of course as this will control the wind. tested with unity 5.6.3.