If the hip were to hit the bar while comming up and foward while the athlete pulled the bar up and back, the bar would travel straight up. The contact with the bar would then appear to be a brush regardless of how hard the contact was.
Here is a thought experiment. Thread a 10 ft rope through a 10 lb plate. Have two guys stand just far enough apart that the plate rests on the ground. If both pull backwards on the rope simultaneously, the weight is launched straight up and with a velocity much greater than could be achieved by pulling up alone.
This may not be the physics of ideal technique, but it ought to be considered in light of what videos of record lifts reveal.
Just an amateurs thoughts.
On another note, one of our trainers was training at the Olympic Training Center on the Olympic Lifts and having fair success. Days later she noticed in the shower that the girls with the big lifts all had bruises on their upper thigh/hips. Armed with that insight she quickly moved to the top of the class.
Coach said she should have gotten pictures!