[Rules] Terrain Clarification

[PzIVF2]

With respect to the map terrain for Fall of France and Road to Dunkirk, and similarly the Eastern Front games (FitS and Kursk) - how does one determine what is "clear" terrain, versus "brush, tall grass"?  Plowed and sown fields are straightforward, but I can't tell - and see no discussion in the game scenario prefaces - whether the plain green hexes of Fall of France and Road to Dunkirk, or the yellow hexes of the East Front games - should be considered "clear" terrain or brush/tall grass.  

I note that the hill tops on map 43 - 0415/0516 and 1102/1201 - seem 'clear' to me; whereas I expect the yellow hexes everywhere else to be steppe, with corresponding movement and sighting costs.

My default assumption is it is all brush or overgrown grass.  

Thanks,

rt