Yeah, I spose it goes both ways, but I still think that native speakers do have a pretty big advantage, which isn't fair to the rest of us.
Ok, they didn't learn the grammar like we did perhaps, but in exams you generally don't have to know the specifics of the grammar, but how it works - things like word order, tenses, cases - which you'd learn from speaking. So they'd still have an advantage. Besides, they'd still have to have studied it in class, right? So they'd learn the same things as us, plus have the advantage of knowing all the vocab, tenses, cases, without having to think about it.
The english components of exams are pretty basic, don't you think? And you shouldn't assume that their english will be bad. I'm a native Turkish speaker, but my english is much better than most people in my school. I think if I did Turkish, after learning the things in class, I'd be much ahead of non-native speakers.
Basically native speakers do have an advantage, and it's up to them whether they use it or not. They could be lazy and fail, but if they're choosing to do German they'd probably excel in it - I think there should be a background speakers exam.
Well, I'm going to Germany for 10 weeks later this year - I'll let you know whether I think that gives me an advantage (hmmm, if so, that could end up being kinda hypocritical)