Hair dynamics and angle of collision

Hi, i did some experiments and got this results in Blender 2.76b.

  1. hair particle passes through plane with no collision
  2. if i extrude edge(angle >45 degrees) on which hair “plans” to pass through then collision happens
  3. if angle is less than 45 degrees than nothing happend
  4. any other edge wont help

(both green are plane and emitters)

Am i missing something here or this is supposed to work like this?