An iterator uses an array, and in your example you had just 1 element in the array, albeit with 3 collections. So the iterator would iterate just once over the elements rather than iterating through each collection.
The get/map technique is very useful when looking through collections/objects for a specific item. the get(<expression>;1) can also be replaced with first(map(<expression>)) where first just chooses the first element of the returned array from map().