Usually when a car is run on a dyno it will be a run through a single gear (4th or 5th, typically the gear closest to 1:1 is used).
The graph plots power vs RPM (either dyno roller RPM or calculated motor RPM); by the time the camera started to pan up, the motor and dyno roller was spinning down from its peak RPM and therefore all the data displayed had been captured. The graph could easily be doctored, of course, but assuming it's not..
Power is basically proportional to torque times RPM. A linear power curve as seen here (and also for most of the Zero dyno above) means that the torque is flat, eg you get the same amount of force at the wheel no matter how fast the motor is spinning.
It's reasonable to assume (but retain suspicion) that the dyno has been calibrated properly - but just because the motor is mounted on an Engage doesn't mean that what we're seeing is (or is not) the shipping-intent Engage motor. SMRE could be using the Engage as a testbed for new motors.
For example, the Empulse motor. We've long been told that the Empulse motor is 40 kW (peak). The recent LATimes article at the Long Beach motor show indicated that we might see a bit more power. 40 kW peak motor power is about 54 hp; 49 hp at the wheel is pretty good.
Compare to the Enertia, which is rated at 13 kw = 17.4 hp. If the dyno is accurate, then roughly 77% of the rated motor power is available at the wheel. Using the same ratio for SMRE's test gives a motor power around 64 hp, or 47 kW.
Does the Engage have a 47 kW motor, or is this something else? I'd like to know : )