Is undo-tree dependency strictly necessary

I was wondering if undo-tree is only there to match Vim behavior, and if I could use Evil without it. I actually find built-in Emacs undo functionality intuitive and I'm used to how it operates. On the other hand, I've run into some cases where undo-tree didn't behave as expected. If there are no ill consequences in using original Emacs undo vs undo-tree, it would be nice if it were configurable. --Leo P.S.: Thanks Frank and Vegard for quick bug-fixing action!