Much of the torque is reduced to the 3 pth by lowering the winch so that the winch "blade" / plate digs into the ground. You get an idea of how much this helps if you ever set the blade on ice, or a tree root, or a hard surface and get the surprise of the tractor getting pulled backwards instead of the log forward. (BTW: Winching in 4WD instead of 2WD was once the answer to prevent tractor sliding when winching from pavement)
Many winches have a pulley mounted down low that you route the cable through to redirect the pulling forces from the top pulley and off of the top link. However, there are some advantages of pulling directly from the top pulley as it lifts the log more as it's sliding over roots etc..., but it does put greater stress on the top link than running the cable through lower pulley.
On pulls for big logs I run cable through lower pulley, but realistically I don't worry about breaking top link. I'm sure it's strong enough to lift the front of my tractor up before it ever broke.