A couple of observations: If you Define it as a , Custom Shape, and use that to drag out with the Shape tool, the controls do .show up in the Properties panel. Getting the size and placement of the dragged-out Shape right would be a pain.
Also, if you have a "non-pen"Shape, with the controls in the Properties panel, setting the Pen to Combine Shapes will cause the controls to disappear as soon as you lay down the first point.
I can't see any reason for this behavior, so I would agree it's a bug.
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