The S9 is literally on the same platform as every other S-Bahn train that goes from Hbf to Alexanderplatz, so you'd also have to willfully ignore the ample stat

The S9 is literally on the same platform as every other S-Bahn train that goes from Hbf to Alexanderplatz, so you'd also have to willfully ignore the ample station signage for all the trains that pass you by.