Do Animation curves have some stored offset? Blender 2.79

Question

I have an odd problem. I am exporting a scene, including animation curves. I have parent/child relationsships in my scene.

Base example: I create a big cube at the origin. I add a small green cube as a child of the big cube, offset z +2. I hit I to create a location keyframe. On a later frame, I shift the green cube 2 in the x axis, and take another location keyframe. And later again, I move it -2 on the x axis, and take another location keyframe.

Here is the result:

The graph shows exactly what I would expect: the X position of the green cube goes from 0 to 2 to 0.

However, let's repeat the process, except starting with the big gray cube at offset 4. Create a cube at 4x,0y,0z. Add a red cube at 4x,0y,2z, and make it a child object of the cube. Create the same location keyframes: frame 0, x = 4. frame 30, x=6. frame 60, x = 4.

So this shows the X Location in the curve as starting at 4, going to 6, and back to 4. This is not what I am expecting! Because the parent object is already at 4x, I was expecting the child object to go from 0x to 2x to 0x.

Now here's the fun part: Let's say I move the gray cube back to 0,0,0. Unexpectedly (to me at least), the red cube's curve stays at 4 to 6 to 4! In the scene, the red cube is moving from 0 to 2 to 0, but the curve says otherwise! Clearly there is some sort of offset saved in the curve!

So, my exported scene gets all messed up unless I happen to position my parent object at the origin before I start taking keyframes, which really is not practical.

For what it's worth, here is my code to export the animation curves:

scene = bpy.data.scenes['Scene']
fps = scene.render.fps
# Export actions that match the format "[name1]name2"
pattern = re.compile('\[([^\]]+)\](.+)')
actions = bpy.data.actions
fw('<animdata>\n')
for actionname in actions.keys():
    match = pattern.match(actionname)
    # Does the action match [name1]name2 ?
    if (match == None):
        continue
    action = actions[actionname]
    # Grab the [name1] portion of the action's name as the object name
    obname = match.group(1)
    # Grab the name2 portion of the action's name as the Action name
    shortname = match.group(2)
fw('  &lt;animation name=&quot;%s&quot; fps=&quot;%d&quot; start=&quot;%d&quot; end=&quot;%d&quot;&gt;\n' % (shortname, fps, scene.frame_start, scene.frame_end))

# Grab the curves of this action.
fcurves = action.fcurves
if (len(fcurves) &gt; 0):
    fw('    &lt;anim object=&quot;%s&quot;&gt;\n' % obname)
    # Write out each curve as a &lt;curve&gt; element
    for curve in fcurves:
        fw('      &lt;curve path=&quot;%s&quot; axis=&quot;%d&quot;&gt;\n' % (curve.data_path, curve.array_index))
        for kp in curve.keyframe_points:
            fw('        &lt;point interp=&quot;%s&quot; co=&quot;%f,%f&quot; lh=&quot;%f,%f&quot; rh=&quot;%f,%f&quot;/&gt;\n' % (kp.interpolation, kp.co.x, kp.co.y, kp.handle_left.x, kp.handle_left.y, kp.handle_right.x, kp.handle_right.y))
        fw('      &lt;/curve&gt;\n')
    fw('    &lt;/anim&gt;\n')
fw('  &lt;/animation&gt;\n')

fw('</animdata>\n')

Thanks for any insight!