This is all 100% genuine, as a dyno dynamics operator I am aware that there is an issue with 5 cyl cars and we test in the exact same way as this test was carried out.
The DD dyno is a very complex bit of kit and has various calculations built in for transmission losses based on the amount of cylinders, when testing a car you must input the amount of cylinders and the dyno will calibrate a transmission loss and a ramp rate (the speed of allowed acceleration against the load placed on the tyres by the dyno) but there is no option for 5 cylinders, so you test in 4cyl mode and then 6 cyl mode and use an option known as graph averaging that is built into the dyno to determine the true BHP.
However, none of the above will affect the measured power output at the wheels. The calculations and compensations mentioned above will only affect the given estimated flywheel power.
Does this really matter? not at all. Its great for a number on a bit of paper but the car drives out performing in the exact same way as it drove in. Above everything a dyno is a tool that should be used for measuring a difference in power before and after modifications or during mapping, the number at the top of the screen is a by-product of lots of guesswork made by the dyno, albeit a very highly developed guess that has resulted in from of research and testing by the dyno operators.
Its power @ the wheels that counts.