Guillaume Laferriere

Give it a try with this scene.

You need to access the control_data output of the rig in order to extract the animated transform values.
I'm using a wrangle to get the xform output values of each TransformObject from the @parms dict detail attribute and stamp it to each point transform. If you inspect the geometry spreadsheet of the invoke_get_animated_control_parms node, you'll also notice you have access to the other output port values of the TransformObject nodes.

Look for hou.ChannelList.addGeometryChannels() in the hom documentation. It allows you to put the channel in the animation editor.
You’ll also need to call hou.playbar.setChannelList().

Ok, so finally I was able to fix the problem and export the animation properly.
I made a small video explaining the steps I had to do to fix the problem.
My initial feeling was that something was broken on the baking side, but it turned out the controllers were not properly driven by the animation.