That's not true. The proper military use of flashbangs is to throw them into a room (to land wherever, usually the center of the room) and then run in and murder everyone inside. You are overstating the precision involved.
I guess its a moot point to try and explain the concepts that are common to almost every CQCish type training out there.
The point is you don't throw a flash-bang and grenade at full power. Knowing where the center of the room is and even if that's the best place for it to land is not the easiest thing in the world.
Nearside corners people, most people that are under a threat will be closer to the corners than the middle of the room and the corners that will give you the most problems to due the amount of time it takes to clear and how quickly they can ruining your day is throwing stun grenades to get effects on the nearside corners.