I think there are always cases in the States that people cannot make it to Hanover for some reason. I've heard that people who are outside of the country has more of a reason; however, take me for an example. I live and work in San Diego. I'm pretty much at the very very very opposite of the states from Hanover. If I didn't self-initiate, would it look bad? I really don't think so. I'm about 20 minutes away from Mexican border and there may be someone in Tijuana Mexico who's applying. If he/she didn't self-initiate, would that be bad? I still don't think so. I think it's judged case by case. Now, for a person who lives in Boston or New York, I think it'll be harder for htem to justify why not self-initiate the interview. But for someone who's literally thousands of miles away from Hanover, I think it'll be okay to not self-initiate.
just for the record, I did self-initiate and wrote a long debrief about it on one of the earlier pages.