"Are you students?"
Translation:Ti diákok vagytok?
Exactly. "Egyetemisták" is just a small group of them. Those are university students. That is why it was not accepted.
Well, if a sentence says "food" and you translate it as "kenyér" ("bread"), should it be accepted? Bread is food. Right?
It is the same with students, a very wide group, and "egyetemisták", a very specific group of students.
It might be worth pointing out that, in some languages 'student' means only 'university student'. This is not true in English, which may be the source of VojaJ's confusion.