OP, as long as you have more good reports than bad ones, you don't have to worry about your reporting accuracy too much. Once you have more than 300 good reports, you will be able to see your report history, which will help you to learn from your mistakes and improve upon future reports. Just keep reporting!
That's a good report if you ask me. By reporting a thread to be moved, what you are saying is this thread doesn't belong in this sub. Please take a look at it and consider moving it to sub X. The fact alone that you are correct and the discussion doesn't belong there should be enough for your report to be marked as 'good'. Maybe you were wrong about the final destination, and that decision in on the moderator, but you were right about where it doesn't belong.
That's definitely how it works as I quite often report topics to be moved and sometimes mods move topic in another board and not the one I suggested is the right one and it still gets marked as good.
As a matter of fact, you don't even have to mention where topic that you are reporting should be moved if you are not sure. Its enough just to report it and write that "topic doesn't belong in this board" or something along those lines and if mods agree with you and topic gets moved, it will be marked as good.
I follow this same policy. When I'm not sure where a discussion thread should be moved, I leave that decision to the moderators. But I also do everything I can to make their jobs easier, so for example, when it comes to reporting multiposting, I always refer to other posts so that the moderators don't have to look through the user's history.