Translation:The boy is sad because his finger hurts.
If you would accept sentences with a virtually identical meaning where do you set a limit?
- Oranje en groen - Should you accept "Green and orange" as a translation? After all both colours are there. Though what if they got the translation of the colours mixed up?
- He goes to the school - Should you accept "Hij gaat naar de universiteit"? After all a university is also a kind of school.
- Mijn been doet pijn - Should you also accept "I have an ache in my leg"? After all, the outcome of both sentences is the same.
Yes, ideally all those should be acceptable alternatives. I've certainly been caught out with ordering before (e.g. orange and green vs green and orange). After all it doesn't improve my Dutch to be penalised for something like that, it simply causes frustration. However I accept that there are limitations with the software and with the time of the course contributors, so this ideal world I imagine is not necessarily easily achievable.
Perhaps they show you may understand what the sentence means, but Duolingo is not just about knowing what a sentence means but also what the words in a sentence mean.
To take my last sentence:
- Mijn been doet pijn - My leg hurts - Shows you know what the sentence means, what "mijn been" means and what "pijn doen" means
- I have a pain in my leg - Shows you know what the outcome of the sentence is, but it would seem that you don't know what "pijn doen" means in English.
Or to take my example with school vs. university. If you say that should be accepted you could also accept Ik zie een eend as a translation for I see a bird. After all a duck is a bird and the sentence leaves open what kind of bird you see. Although it would very much seem like you would not know what the translation for bird is.