Sorry, I meant in the low speed, high acceleration regime (maybe easily confounded with takeoff?). There the engine will turn one motor to generate electricity, which will then power the second motor, like a series hybrid.
There's a video linked elsewhere in this thread that explains how the toyota system works, it's worth watching as it clears up several common misconceptions about the system.
... and instead drive one of the motors, generating electricity to power the other motor to push the car forward.
I feel like that video you're mentioning did a poor job if it didn't describe one of the more important and clever aspects of the Prius's design.