NOTE: also OrderedDict currently uses trashcan hacking to work around this problem:

    /* Call the base tp_dealloc().  Since it too uses the trashcan mechanism,
     * temporarily decrement trash_delete_nesting to prevent triggering it
     * and putting the partially deallocated object on the trashcan's
     * to-be-deleted-later list.
     */
    --tstate->trash_delete_nesting;
    assert(_tstate->trash_delete_nesting < PyTrash_UNWIND_LEVEL);
    PyDict_Type.tp_dealloc((PyObject *)self);
    ++tstate->trash_delete_nesting;

So this seems to be a known problem which deserves to be fixed properly.