I see it as Cabrera's rear arm is in the process of being extended going into & through impact.
Cabrera doesn't have the 'lightning' in his swing like these hitters:
Atleast 'good old' Pet has change alittle bit:
However, he is wrong about extension. He is correct in his video that the elbows should stay the same distance apart as the upper body rotates. However, as the upper body rotates powerfully in his "power triangle" position, at some point before impact with the ball, the velocity of the rotation will naturally cause the elbows to extend fully at or just after impact