Projections using dot notation to select an array element don't work

 db.getCollection('SomeCollection').find({}, {'array.0':1}) 

I would expect the above to return documents like:

 {array:[{a:'a',b:'b'}]} 

but instead returns all elements of the array, just as empty objects:

 {array:[{}, {}, {}]} 

This doesn't make any sense. It seem broken.