Yeah, the power curve chart shows very little power being made as the RPM's get higher. On mine, and on a tesla roadster.
My understanding was the same as Daox. They have very good low speed torque but kind of putter out once spinning. My experiences with both of my electric bikes and my modified 1350 watt electric scooter back this up.
Back on topic, I thought that using the gas motor was more efficient at higher speed than the electric motor. Hence the use of "some gas" at that time.