Think about it like this...Maybe, but this: The battery is charged by only two things; the regen braking and the engine. If the engine is charging the battery, or the battery is being maintained (not being used), how can electric motors which run on electricity get their power.
I know from butt dyno that hybrid has tons of torque when I hammer it, and e-save mode just has the rpms running high for less power.
Have you noticed when you're at <1% you still get the added power from the electric side when needed? You get it at slow speeds and under high load. Yes, you use more power from the ICE, but you still have battery in reserve for on demand usage.
The battery read out (<1%-100%) represents one compartment of the battery. When you run in eSave to maintain the charge (or recharge), this is the portion you're maintaining (or recharging). You still have the reserve that the system normally has at it's disposal.
You always have that extra power, even in eSave mode. It's a separate portion of battery power that (I believe) is always being charged/maintained by the ICE as needed.
Real world example... I drove from Daytona Beach to Baltimore and back. If this reserve wasn't being maintained by the ICE, there's no way I would have had any power to draw on from the battery side of the house, and yet every time I needed to pass someone, that power was there. Watch your meters, in eSave, even on an empty battery, when you floor it, you still see power from the electric motors. Yes, you get higher revs from the ICE, but you aren't without the electric side of the propulsion system.