Not a native speaker, and this is a just an anecdote so it may be inaccurate. When i visited spain, my friend from mexico told me its a regional thing. He said that "qué tal" was the way you greeted someone there, rather than "cómo estás" because that was just the way the people talked there, the same way people in english greet people differently depending on where they're from. But obviously both are perfectly acceptable, pretty much anywhere you go.
Although if it gave you the english and you translated it "hola, cómo estás" and got marked wrong, the question is wrong lol, so just report it
I may not be a Spanish expert, but I live and work around Spanish-speakers. I make frequent trips to Mexico and Spain. I've heard "que tal" countless times, but I've never heard "que tal estas". It almost sounds redundant, like the "estas" is already implied.