1 - It's badly named as it contains more than the coordinates of the pointer. It has also id, tool_type. So why not call it simply "pointers"?
2 - There's no way of telling which axis is defined/exists and which is not. E.g. some devices provide touch_major and touch_minor, some do not. Likewise for pressure, orientation, etc. So, if you have a device that does not give, say, pressure. How do you fill you pointer_coordinates[i].pressure? with zero? That's a lie as 0 is a valid pressure value. And then, when reading MotionEvent.pointer_coordinates values, how do you tell if a given value was really reported by the device or if it just has its default value set by Mir? android::PointerCoords, for instance, has a "bits" variable that you can check to see which axes are present/defined.
Sounds like two distinct issues, but close enough I guess we could keep it as one bug... ?
See also: bug 1175362