Wooooow literally the only spot I glanced over...From the article
For our test, we headed to Livernois Motorsports and Engineering in Dearborn Heights, Michigan. We strapped the Supra to the Dynojet all-wheel-drive dynamometer, as the car's stability systems only play nice when all four wheels are spinning. For this observation, we ran the test in the eight-speed automatic transmission's fifth-gear ratio of 1.32:1 to achieve a full sweep of the tachometer.
Not sure what’s unclear about all 4 wheels spinning. The rollers are likely mechanically coupled unless they are using electric motors (unlikely) due to complexity in maintaining synchronized speeds of front and rear drums