It does, but, in this case, it emphasizes the question. A good translation would be: "Is he really coming?" See how "really" is doing the same job here? You'll get the hang of it as you dive deeper into the language. Brazilians are extremely casual, so... Learning informal Portuguese is highly recommended!
Does Santa really come every year? Does the Tooth Fairy really come for for my baby teeth? Does the Easter Bunny really come to hide eggs?
I know, "really" with these imaginary beings is a bit oxymoronic but you could use it with movies such as, "It's a Wonderful Life" in saying, "Does Clarence really come to help George understand how valuable his life is?"
Or in real life, "Does he really come to help feed the homeless every week?"
Does he really come to play golf every weekend?
You want an apple? as a echo question is not slang.
That said, it is indeed an "echo question" and not really appropriate for all situations, especially language learning. Most especially because Duolingo does not really pay attention to punctuation (other than accents) and cannot discern intonation. So, Duolingo also does not accept this form, at least in the PT trees (and I am pretty happy about that).
The question has been kind of asked, yet never answered:
how would you say "Is he even coming?"
As in, for instance, a conversation where we talk about a guy and how he could behave during some specific event, then someone asks "But hey, is he even coming in fact ?!?"
And so, by the way, how would you say "He is not even coming" ? Ele não vem mesmo ?
Muito obrigado !