Should nixos-generate-config include fileSystems?

When I run nixos-generate-config --root /tmp I would expect it to include fileSystems?

When I look at df -h, I see it has a label that it uses. Is that maybe the reason why I don’t see anything in hardware-configuration.nix?

Filesystem                             Size  Used Avail Use% Mounted on
devtmpfs                               393M     0  393M   0% /dev
tmpfs                                  3.9G     0  3.9G   0% /dev/shm
tmpfs                                  2.0G  4.4M  2.0G   1% /run
tmpfs                                  3.9G  320K  3.9G   1% /run/wrappers
/dev/disk/by-partlabel/disk-main-root  916G  2.1G  867G   1% /
/dev/sda1                              511M   42M  470M   9% /boot
tmpfs                                  785M     0  785M   0% /run/user/0