2. And you've apparently never used Tower.
And as long as we're being totally unscientific about the whole thing, the most common mistake I've seen when using a version control system has come from people checking in unintentional modifications using the command line tool because it is easy to miss. In a GUI, you can better see what is being committed, and a simple checkbox lets you skip it, while double clicking gives you a diff that makes it so much easier to review every change before you commmit.
Most times when someone on my team screws up a commit, it's because they botched the command line (the inverse of this article's claims). Fix it in Tower in a few minutes in a visually simple way that helps them understand what's going on.
It also makes submodule usage do what you think it should do.