Shard grass, engineered or evolved?

It suddenly occured to me that shard grass (SF-1) is tailor made to keep the ul-mor away. Its likely that the ul-mor are the most susceptable to the damage it does. Its almost as if the eorna desired a fire break between the ul-mor and kurabunga. Maybe not "desired" but perhaps it had been considered desirable. There dosent appear to be any other "fire break" measures in place so perhaps it was just developed the one time and later it was decided that this was unneccessay thus the measure was not repeated.