Why is the wheel bearing grease leaking out of the dust cap?

I asked this question at FBBO before.
Nobody responded to say that they torqued them. All the respondents did the same as I do....we snug down the bearing nut, back it off to the next notch in the thin sheet metal cover and slide the cotter pin in.
Can you imagine though torquing them to 90 Ft lbs after MISreading the service manual?
Our high school shop instructor (a retired Mercedes Benz and Navy mechanic) told us to never "back off" the nut to the next slot. He said that was the "old man" way. He always told us to tighten it up while rotating the tire and pounding on it with the palm of your hand (use the torque spec if you want) and then tighten it to the next lined up slot. It's always worked for me so that's how I continue to do it.