165mm cranks are used on track/fixed gears because of pedal strike. A shorter crank and less chance of your pedal hitting the pavement when cornering hard.
You wouldnt have to worry about this on a road bike because you can coast through the corners.
Thats why I use it anyways.. I have freewheels but never use them.
What size crank a true SS/freewheel has I dont know.