Shouldn't it be "... where one is going TO?". I mean, "wohin" suggest destination, right?
You can also say "Where are you going?". I think the "to" is rather optional here.
fair enough, but am I right about the fact that "wohin" implies destination?
Yes, "hin" implies movement to somewhere.
We are just learning, is it a good idea to throw in philosophical questions like that?
you should not blame duolingo's insight :)