I don't think that's what the economist is saying. If you don't know that they were at the same time, then it could just be that low phone batteries and high Uber prices both correlate with it being later in the night. They're not saying that Uber is guessing the time you call for a cab based on your battery percentage. Obviously Uber knows when you're trying to get a ride because you contacted Uber to get one at a specific time anyway.