Yes, that's true, and that's why foreigner need to prove that they're financially sufficient by getting a blocked account around 8700€. This should be enough to cover the average living cost for a year.
(Foreign students are normally a lot richer than most Germans LOL. How many German students has 8700€ in their bank account hahaha).
The student can only withdraw the money around 600-700€ monthly.
However, this amount must be in the bank account again when the time come to renew the visa, that is the standard procedure. ^_^
Whether one meets a very very nice immigration officer who probably doesn't want check your bank account again, that would only rely on your own luck. :-D
To be certain that your visa would be extended, the best option is still studying hard to try staying on schedule and always have sufficient money in this blocked account. :-)
Part time job is naturally a big help, however studying in a foreign language is hard and most students are not geniuses so, one can't work much either if one doesn't want to have a big problem in catching up the class. The drop-out quote in Germany is obviously not so low. :-D