why?
If it doesnt apply on angled buildings ignore me. otherwise shooting from stairs,  roofs etc would be disadvantageous,  as well as attackers using hills.  
also,  stop nerfing the mod ^^  
It would make sense. Standing on flat land gives you better balance. Would this also apply for HA, btw?
dude,  we talking about trained soldiers,  i think they could manage...  did you see the video where the horsearcher shot 3 arrows midair whilst falling of his horse with incredible accuracy?