The summary makes it sound like this is an algorithm tuning problem - "err on the side of too much in focus" - which isn't the case. It's a byproduct of sensor size.
Even with real cameras the rule of thumb is a full frame (35mm film equivalent size) camera, at a given focal length, has a stop "better" depth of field than a camera with an APS-C sensor taking the same picture - so a Nikon D7100 would need to shoot at f/2.0 to get the same blurring as a D800 shooting the same photo at f/2.8.
Most camera phone sensors are rather tiny compared to real cameras.
On a side note... pedants may going to have fun nitpicking all of this apart.