YC, effectively, owns the whole stack (i.e. vertical). Their main selling point is the YC network and being founder friendly to derisk creating startups. YC also created the continuity fund that is where the typical VC comparison would be. I am not sure what the terms on it are but I imagine it is geared only to their companies. This means YC is willing to assume more risk and gives a vote of confidence for their products. It's amazing really to see this grow as big as it has in 15 years give or take.