Oh, I don't think there's any doubt that they can be steered, they do that at marine parks.
About 20 years ago I worked at Sea World in San Diego, and had a chance to play around with a lot of the cetaceans. I wasn't a trainer, but I've had direct experience with bottlenose, Pacific whiteside, pilot whales, beluga, and killer whales. They're very doglke, but there is more happening upstairs than there is with canines. Cetaceans have an advanced play instinct, a much greater capacity for calculated mischief, and also for the spontaneous creation of games with basic rules. I'm not at all surprised that there is an element of unpredictability with the Navy's dolphins.