How is pre-rotation calculated with respect to Rotate Axis? Inconsistent to Post-Rotation which always matches Joint Orient

[ilan.keshet]

Below is a picture of a joint's transform in bind pose: 

in FBX going to the joint, and printing out the Pre-rotation / Post-rotation: we see these values:

Postrotation: x: 73.67505 y: -58.60028 z: -16.32495

Prerotation: x: 180.00000 y: -5.48677 z: 0.00000

As you can clearly see, -- pre-rotation matches Joint-Orient,   while Post Rotation does not match rotate axis. 

I've tested around in Maya, -- and Joint-Orient and Rotate-Axis always have rotate order XYZ. 

How do I convert this Postrotation into the viewed Rotate Axis of "-80.264   30.0000  -54.736"?

[ilan.keshet]

One thing to note:  

I have tested using the values in Post Rotation (that don't line up with Rotate Axis) using the FBX Matrix Transformation, and it seems to animate correctly -- Though I still have no idea how the Rotate Axis is calculated from the Post Rotation or other values.