The BNO055 data sheet says that the magnetometer z axis resolution is 15 bits whereas the x and y axes have 13 bit resolution (default values). Why z axis is treated separately? What is the intuition behind providing higher resolution to z axis values?
What is the intuition behind providing higher resolution to z axis values?
Did you ask the manufacturer? I guess if intuition was the reason to make it this way it was the intuition of someone there and if that person does not read here we cannot tell.
In normal usage the z-axis has the lowest values so it might make sense to have a higher resolution there. But I don't know if the manufacturer did the same considerations.
I assume, the Z has higher resolution is because of packaging. Each axis has its own sensor. Each sensor is the same type but not all have the same amount of room inside the device. The Z axis may have the most favorable orientation inside the package.
So, you can mount the package where the Z is on the axis you are the most interested in.
Cheers