It wouldn't be from dead ahead but pretty close. In the video the boats are changing direction but as their speed is high even in the turns the apparent wind is still from way ahead of the beam. You are having trouble judging the tack they're on because at their speed they are close hauled all the time. The sails are cut pretty flat and sheeted in all the way. That rig wouldn't work on a slow boat. In their case one sail doesn't blanket the other but it would in a slower boat. The record breaking multihulls act the same way. They tack downwind with the apparent wind well forward of the beam. Notice on these 2 boats how they are sheeted in as well. After they reach a high speed they create their own wind.
Living aboard in Victoria Harbour