They want a signature on paper in case you're not you.
Now the coversheet for the exam has a place to write your name and sign it which you must do before starting the test.
The older brother signed it as his younger brother. Then was charged with forgery. The requirement to sign was there to make that kind of cheating a crime.
German source https://www.welt.de/wirtschaft/article191846877/Hotelanmeldu...