Fifty percent duty cycle (per winding) is feasible if your load draws light current. Light load brings out the ramping-up effect as each pulse goes through the primary.
However the tendency is to load the secondary by taking greater Amperes, such that square waves go through the primary. In that event It's not easy to observe saturation. One indicator is when efficiency drops severely. Supply power reaches a point where the flux field fails to build beyond a maximum point. The excess power does not convey through the transformer.