Rotation to Basic 0-360 pitch, roll, yaw

Questions
5

Ok. So I got the correct orientation, while again, having to add +90d to the UP axis, which is now X, I think.

	camera.rotation.reorder("YXZ");
	cameraRotation = ( Math.round( THREE.Math.radToDeg( camera.rotation.z ) % 360 ) ) + ' ' + ( Math.round( THREE.Math.radToDeg( camera.rotation.y ) ) + 90 % 360 ) 
		+ ' ' + ( Math.round( THREE.Math.radToDeg( camera.rotation.x ) % 360 ) );

This yields the correct result! But… why? Blender uses XYZ Euler and Terragen uses XYZ Euler just +Y UP and +Z Forward being the difference, but this is set in the FBX. So why is the order Three.js uses XYZ wrong?

What does this mean for people choosing any other Euler order and detecting this problem?