Elbows Bend, Power Ends

Is an early arm bend during the pull truly incorrect Many coaches use the term elbows bend, power ends. The thought process behind this theory is that once the athlete bends their arms before finishing the pull, this can decrease the acceleration on the bar. Some times an early bend also causes the lifter to pull themselves to the bar, causing their chest to pull forward, not allowing for a vertical extension. While all these thoughts are valid, I feel like in few cases an early arm can be acceptable.