Janna Ultimate Destroys Super-Minion Pathing

I was in a ranked match where my team took all three enemy inhibitors. The enemy Janna then proceeded to cast her ultimate at the nexus. All minions were pushed back as expected however, super-minions were not able to continue after the ultimate. They continually walked left and right while remaining in the same position. My minions were now unable to attack the open nexus. They began moving once again when an enemy minion or champion came very close. This can be very game breaking when all that is required is one hit to the nexus from a minion.