I wouldn't make too much of the resolution of the Sensor.
There are all sorts of reasons to use one sensor over another.
Maybe the dynamic range is better
Maybe the low light sensitivity is better
Maybe you just want to unify all the cameras around the same sensor
If you need a full resolution image for your application you put it into that mode, and if you don't need the full resolution image then you bin it down. Binning is pretty cool because it can (as it not always) significantly improve the sensitivity because it's essentially creating super pixels.
The Sensor resolution doesn't tell you anything about the actual working resolution.