Single Phase Full Bridge Inverter - I Can't figure out which PWM Control Technique is used
This method is referred to as discontinuous mode. It is extremely beneficial in reducing switching losses. 

Do AC inverter H bridges ever get driven this way?

3-Phase Inverter Control with SPWM(Sinusoidal PWM) for 3-phase sinusoidal output

And and external paper discussing the concept
http://www.wseas.org/multimedia/journals/circuits/2016/a305801-572.pdf