It's also totally conceivable that they ECU is programmed to reduce or more slowly apply engine torque in 4-LO situations that usually break the diffs. That would be super easy to do for the electric assist and turbo boost. GM used to do that on their HD trucks in the aughts - "torque management" - as a way for them to keep from blowing drivetrain components.
This past weekend our Hybrid Highlander really surprised it when it chirped the rear tires pulling away from a stoplight at full throttle (ended up not in the turn lane and had to drag race other traffic to be able to merge
). From having 25K on our "real" Toyota hybrid (integrated unit rather than a simple power-adder), the only time the electric assist really makes it's presence noticeable is in those full-throttle situations.
This past weekend our Hybrid Highlander really surprised it when it chirped the rear tires pulling away from a stoplight at full throttle (ended up not in the turn lane and had to drag race other traffic to be able to merge
