No such thing as unicorns either, but we can still speak of them! There is nothing wrong with DL's sentence as it stands, it just isn't one you hear very often. But to be fair, 'development' is one of the synonyms offered in the hover hints, so yes I agree that should be accepted.
In some ways I prefer these kind of curveball questions, because they really make me stop and think. Then I have to make sure I have understood the meaning, rather than seeing a phrase I recognise and just tapping that out without breaking it down. Although admittedly, many of the more idiomatic expressions are a leap of blind faith :)
Is there really any difference between development and evolution? These are two of the drop down hints, confirmed by dictionaries, but the owl chooses to ignore "development" and issues strong warnings against confusing the two words. He does, however, allow present and preterite translations of "hablamos".