This happens only the first time the feature selection is done and here is the reason why this happens:Map has two types of selections - Feature Selection and Graphic SelectionThe first time you select a feature, map first replacec the Graphic Selection with Feature Selection as its active selection - this is when it first fires the evern saying selection changed. Then it actually replaces the feature selection with the new selection. Once the Graphic selection is replaced by the feature selection, it no more fires this events twice. For 9x this is a known limit.