Earlier quoted context omitted.
I often type "git clone ", then switch to a browser to copy/paste the URL, which is usually fine, but there are still many times where I've happened to include "git clone" in the copied string. (So I end up with "git clone git clone $URL").
That danger doesn't apply when things are copied from the browser chrome (address bar) or other locations. So why would pasting then still be dangerous?
I think blindly passing on advices "because $SECURITY" can actually detrimental to security because you may end up with half a dozen esoteric practices without actually knowing what they defend against. (I know the parent was half-joking, I think that's a more general problem)