The problem with Berto is that he fights in bursts and only really has a chance to really be effective when he hurts Quintana which probably will end up winning him the fight anyway; unless Quintana starts controlling distance better and popping jabs like they're going out of style.
I think he had to. If he sits back too much, Berto's just gonna mug him on the ropes. He's gotta keep shooting sharp lefts down the pipe. Try to catch Berto coming in, which is a strategy that has worked for others as well... particularly Southpaws.
This is when Quintana will be dangerous. Berto is starting to tire, throwing single shots. I see drama coming in the rounds to come.