This style of lunge is actually slightly better than the forward lunge when it comes to building muscle, partly because it's harder to compensate with the lower back, so your form is better.
If your goal is to build your quads, this reverse lunging style also beats the forward lunge, which is better for glutes and hamstrings.
Scott Abel says that maximum load isn't the same thing as maximum weight and he wonders why most people don't get this. How much you can lift isn't the deciding factor; the deciding factor is how much stress a muscle endures.