I disagree. Duolingo tends to balance between common sense and all the possible translations/situations. I don't know where you live, but in Belo Horizonte (for those who don't know, a big brazilian city) we use much more 'parabéns' than 'feliz aniversário' for a birthday compliment. And Brazil's 'happy birthday to you' song is sang 'parabéns pra você'.
Do Brazilians use "Menino" this way as common speech? In American, you would never say "boy" to an African American unless you wanted a punch in the mouth, as slaveowners and Southerners would call a black man "boy" as an insult meaning that they were inherently inferior to a white man. We would only use "boy" if we had an affectionate relationship with the person.