just wait and see what happens when you hit some (invisible) volume limits with fiat deposits and withdrawals...
got my assets frozen for a week and a half while I was travelling europe. awsome experience.
but to get back to OPs issue:
They are simply scared shitless, that someone might actually steal customer funds so they are overshooting a "bit".
bitcoin.de is a great place, but it is a market place, not an exchange so that comes with its own set of issues (forget trading apis and other fancy stuff).