Never seen a tow and a push like that interesting....
I've seen that before...where they were concerned about safely navigating constricted channels with a load that has a lot of windage. If they are set to with a cross-wind, the lead tug will prevent lateral drift as they steer the course. With just the push tug, a significant cross wind could quickly set him well to one side; able to maintain heading but not correct for drift.
That said...I'm sure that the rear lashed tug could have handled the barge under most circumstances, with an eye on the weather. So I'm guessing the fact that they are using two is mostly to be "100%" sure...