groupadd
AccountsPackage: passwd
Creates a group, and nothing more. The right it stands for is built afterwards: a directory it owns, a chmod g+s, accounts added with usermod -aG.
What its options do in the lessons
From the same glossary the lessons render under their commands, so the two cannot disagree.
groupadd -f- Exits with a success status if the group already exists, instead of exit 9. This is
groupadd's repeat-safe form;useraddhas no equivalent.