The reason why Cory wants to hitch on Uber is because he knows people trust Uber more than a random app they've never heard; he says so himself, when he recounts his Shanghai experience. So you'd find the driver on Uber (borrowing its trust network) before switching to the other app. But that also shows why his argument against Uber is flawed: they can charge more money because they actually provide a better service by being available worldwide, unlike these local apps. If the Meta-Uber were to kill the host, it would destroy itself.
But people who don't trust the other app are not going to use the other app anyway. If you want to hire a co-op driver, start with the co-op app first. Hoping Uber will accidentally send you a driver who also happens to be in the co-op seems like a pointless exercise.
As a rider, I need to trust the app to do two things: give me a decent driver and provide me with a reasonable estimate of the cost of the trip. By first making the reservation with Uber, I can get both of those from them, making me much more willing to use the local app to do the actual transaction.
