I am going to add my two cents here. As users of Duolingo it is our privilege to improve the program by reporting "my answer should be accepted" That is how the program learns. It may take some time if the answer is worthy of being included among the other correct responses someone will eventually send you an email saying "you suggested this and we now accept it. Thank you for your contribution." I have a whole email folder full of hundreds of those in all of the languages I am studying. Take heart. It works.
I would have to politely disagree. :) It is like how a square is a rectangle, but a rectangle is not a square. A «bambino» (baby boy) is a «ragazzo» (boy) just because he is not a «ragazza», but a «ragazzo» (boy) is not a «bambino» (baby boy). Call any Italian-speaking 10-year-old a «bambino», and you will witness the indignant response you would get. :D