Translation:Those people who are rich are flying over the mountains.
Because that's sort of the opposite of what the Hungarian sentence says.
Your sentence talks about people who are rich. (Who is rich? The men who are flying over the mountains.)
But Duo's sentence talks about people who are flying over the mountains. (And who is flying there? Those who are rich.)
It's like the difference between "I eat what I see" and "I see what I eat".
I agree with mizinamo. The Hungarian sentence has 'repülnek' in the main clause and 'gazdagok' in the subordinate clause. As it's not unnatural to keep this the same way in English, I see no reason to accept it the other way around. If anything, it could cause confusion by not defining clearly how the Hungarian sentence is built. And while the difference in meaning is subtle in this case, often it's not so, so it does matter what you put in each clause, you can't just mix them up (see mizinamo's example).
But yes, everyone can report what they feel to be correct and let the contributors decide. They have the final say in it anyway.
The correct solution does not sound natural in English. We would not say those, but rather the. Also, it is important to remember that although word order is very important in Hungarian, it is NOT in English. So, it totally means the same thing to say, "The people who are flying over the mountains are rich."
I wrote Those men who are flying over the mountains are rich. So many times it is marking my English sentences as wrong when I don't see anything wrong with it. I thought that instead of reporting a problem this time, I would check to see if this is indeed wrong. I am often just a little different in phrase order. Very frustrating section to get through, as I am communicating the ideas with very small differences and I'm wrong soooo often.