Yeah, when you're flying a multi-crew airplane, you'll hear that kind of callouts. If anyone ever dares to put up the C-17 demo, you'll hear the same thing too. Allows the pilot to concentrate on flying the plane while the copilot watches the instruments and looks for traffic, and the FE works the power.
If you look at the comments, there's a short slideshow that is linked to about who flew the flight and some of the premises of how they do it safely, mainly that once they determined the routine, they made it as simple to fly as possible (for example, only 2 power settings are used - TOGA & Flight Idle) and they have the co-pilot be the safety pilot calling "continue" or "abort" for any deviation. They also flew many hours in the flightsim to practice how to handle any problems that might arise and to verify the performance envelope. It's the kind of planning that allows you to maximize the "wow" factor without actually putting the aircraft at any significant risk.