I think maybe you're confusing terminology. I'd imagine that tzs is referring to the fact that git is a distributed revision control system. Each user (should) have their own local repository. Users commit, branch etc their local repository, and then push to a central repository. You can (and many people do) use git without ever having a central repository to push or pull from.
By definition collaborative git is always multiple repo (unless you're doing something weird like all using the same working directory in a network share, but that'd defeat most of the purpose of git and be a terrible idea). You work on your own repo, and then push changes when you're done.
tzs is right in that what tool I use to manage my local repo is irrelevant to the operation of the repository. Git doesn't mind what tool I used. When it does matter how you're committing is if you're discussing doing things in git - it can cause confusion when someone's trying to find a GUI menu to do something.
The remote server argument's also valid, and probably the best reason to encourage people to use the command line. I've never found a git gui that was better than the command line, and the command line is the de-facto subject of tutorials. I agree with your overall theme of "use the command line".