Agreed - almost every developer I know can code full stack. They are typically better at some parts than other, so they choose to specialize, but the full ability is there. I see it even more often outside of the startup world - in Enterprise IT, you normally not only know the full stack, but multiple products at each level to support all the products that end up running inside a large company. Again, you are not an expert in everything, but you gain a broad knowledge base. And such a knowledge base, held by almost all enterprise IT coders, is hardly mythical.