I just had installed latest debian 11 testing (20210221) with default fs layout (see below).
Additional to the default SW I choosed GNOME desktop environment.
Now after the first start, I'm already getting a warning "low disk space on /"
In my opinion, the question about installed software should be asked before running the partitioner, so it can calculate the size of the filesystems properly.

Here the actual output of df -h:
Dateisystem             Größe Benutzt Verf. Verw% Eingehängt auf
udev                     468M       0  468M    0% /dev
tmpfs                     99M    2,6M   96M    3% /run
/dev/mapper/rootvg-root  4,0G    3,6G  164M   96% /
tmpfs                    491M       0  491M    0% /dev/shm
tmpfs                    5,0M    4,0K  5,0M    1% /run/lock
/dev/vda1                472M     58M  391M   13% /boot
/dev/mapper/rootvg-var   1,6G    323M  1,2G   22% /var
/dev/mapper/rootvg-home   13G     54M   12G    1% /home
/dev/mapper/rootvg-tmp   345M    2,1M  321M    1% /tmp
tmpfs                     99M     48K   99M    1% /run/user/0
tmpfs                     99M    120K   99M    1% /run/user/1000