I was noticing something similar watching an Arguello fight the other day. Sometimes he fires a perfectly straight rocket of a right hand. Other times, he kinds of waves with it, floats it out there. When he would do that, I'd go back and watch a round or so previous to see what the other guy was doing. What Arguello would do is note the move his opponent made to avoid the right hand, then he'd float one out there. And the other guy would duck into a left hook or uppercut. Lopez sometimes does that same thing, to move a guy into a harder punch.
Also, Lopez often has his feet wider apart, looking at him from the side, than it appears they should be. I think he did this because many of his opponents were much shorter, so he could get low and not jab down at them. He adjust for this by kicking his right foot to the right; keeps him balanced and gives his weight a place to go when he punches. When he throw that longer hook, his weight has time/room to get shifted so he can hit pretty good that way. Again, Arguello did a similar thing.