When you rebase one branch, it doesn't move other branches and tags pointing along the history.
You can't rewrite a repository and change your username in past commits, without completely rewriting all of history, creating two parallel histories, and merge conflicts.
Git's mental model makes "moving a branch onto a different commit" (git branch -f) a natural operation. But no graphical tool I've used allows you to do that on a branch you're not checked out on.