DynPhysNodeImpl attachChild()


i need help by some Physics Experts, i am trying to understand JMEPhysics, but there is a problem at

DynamicPhysicsNodeImplementations attachChild() Method:

if ( oldParent != this ) {
      if ( odeGeometry.getOdeGeom() instanceof PlaceableGeom )
          addGeom( (PlaceableGeom) odeGeometry.getOdeGeom() );
           getSpace().addToUpdateCallbacks( new PhysicsUpdateCallback() {

          public void beforeStep( PhysicsSpace space, float time ) {

          public void afterStep( PhysicsSpace space, float time ) {
} );

My Question:

In the first part of the if:(instance of Placeable Geom) I wonder about, how the graphical Geometry is updated, I found no synchronization stuff.

In the else part I wonder about why there is a Callback registered, which serves for synchronization issues, although the Geometry is not placeable, so that i it cannot be moved

Thanks in advance,