I agree with Echo4Papa. The battery always has some reserve to kick in for assist. My use case is perfect.; 19 mile round trip for work, so pretty much using all electric except for longer trips on weekends. About 1500 miles on it so far and the average MPG on the gauge is reading just shy of 35. I'm more than happy with the acceleration on all electric, but hammer it and it's crazy fast.Seems that way. Like I said, I've not experienced any situation where the electric motor didn't kick on to provide extra power when needed, including the 75 mile drive home from the dealer on "no charge".
Now, while cruising on the highway, I'm sure it's running without the electric motors at some point, just like some times it's running without the ICE, but when it needs both, they are both there running and providing the power.