It would seem to me that doing it this way is ideal, because you can run the ICE at one specific optimised RPM. Would the losses from from charging the battery

It would seem to me that doing it this way is ideal, because you can run the ICE at one specific optimised RPM. Would the losses from from charging the battery would be less than those from running an ICE in inefficient ranges? Is the only downside that you can't get a combined peak power from ICE+electric that's higher than the electric on its own? Am electrical engineer, not mechanical, so I'd be interested in someone who knows about these things chiming in.