This belt system is lighter and more reliable than a gearbox system because there are three belts in parallel providing a triple redundant fail safe advantage that a conventional gearbox system does not have. No power is transmitted through the gearbox unless one engine is shut down. The high reliability of timing belts is well known. Failures of these components occur from misalignment, contamination, and shock loads. Alignment and lack of contamination are guaranteed by this design.
Overrunning clutches provide single engine simplicity with multi-engine reliability.
The engines power a common gearbox, which in turn drives both propellers and provides automatic synchronization. There are two instances in which the engines would not operate as one. In the first case, one engine produces so little power that it can't maintain the RPM at which the other engine is running. In fact, it can even be shut off and re-started while the other engine powers the gearbox and both propellers. Two props running at half power produce more thrust than one prop at full power.