I suppose I could see how that could math out, assuming the engine running at an appropriate RPM to transmit to the wheels isn't less fuel efficient than an engine running at an appropriate RPM to generate electricity.

The thing that turns it on its head for gasoline electric though is the IC engine can be almost anything and do almost anything if all it's doing is spinning an alternator with sufficient power buffer before the electric motors. The IC engine could run at a single constant RPM at all times if that's most efficient, or it could be a more car-like thing that adjusts it's RPMs based on load. Or maybe it runs at constant RPMs but the count of active cylinders changes depending on load. The types of engines that can be used suddenly becomes immense because of this too

I just find it hard to believe that the most efficient option for a hybrid is 2 drivetrains. That always struck me like it was more engineers specialized in ICE vehicles simply designing what they know rather than something more bold and imaginative