Bug? reduceComputed invalidated on dependent ManyArray.push

Is reduceComputed expected to work only on regular arrays? For example when dependent on a hasMany association, I’m seeing the property being “incorrectly” invalidated on ManyArray.pushObject().

See console in JS Bin - Collaborative JavaScript Debugging. There are two properties, one on Ember.A() which works as expected, the other on the ManyArray which does not. Notice that initialize is called twice in the latter.