Connection regardless of installation space
In a parallel hybrid, the electric motor is usually placed between the engine and the transmission. On the other hand, a simple gear set connects a torque split hybrid to one of the two sub-transmissions parallel to the axle.
This means the electric motor can be run at a significantly lower maximum RPM, which is lighter and more economical and does not change the installation length of the engine-transmission group.
The hybrid powertrain is only slightly larger than the underlying dual clutch transmission.