I thought that part of it at least was that much like existing life has a harder time breaking down these mirror proteins the same is true in reverse. So any life that was mirror protein based would struggle with consuming and gaining energy. As such the current protein chirality basically won by being first to market. That being said I don't see why that would hamper reverse chirality photosynthesis, and I don't really know what I'm talking about so perhaps your suggestion is more convincing after all.