I'll have to give this one some thought and maybe a little research. Generally when two different words have two different translations we try to keep them distinguished in this course. Qoy is translated as "hear" and 'Ij is translated as "listen". But the words have a complicated relationship in English and it's possible that the Klingon words are close enough in meaning that we should just consider them synonyms and accept them for each other. I'll get back to you on that.
On further consideration, this is an unusual use a of both "hear" and Qoy. This is not talking about passively perceiving sounds, but rather actively paying attention. We are explicitly told that it is OK to use Qoy that way in Klingon and it's very common to use "hear" that way in English, but since it is about active attention, the translation "listen" is appropriate and has been added in this sentence.
English listen can mean just attempting to perceive sound, or it can mean actually hearing and processing the sound. The same is true of English hear. Okrand's explanation happens to be the reverse choices of what you're thinking, but it's not wrong.
The Klingon isn't imitating English; it's choosing only one way. 'Ij means attempting to perceive sounds; it doesn't mean perceiving and interpreting sounds. Qoy means perceiving and interpreting sounds; it doesn't mean only trying to perceive sounds, or only perceiving them.
Yes. There are still some problems with it and it is completely beyond the control of the contributors. But Duolingo is trying to build an automated dictionary. They are also testing a function with some users that if they go to Labs, they can access the dictionary directly.