AD is a way (actually ways) of organizing a computation. There are many different ways to organize the computation and evaluation of a Taylor series at a point.
As an exercise, try to explain the difference between symbolic differentiation, forward mode AD, and reverse mode AD. You will find that there is more content here than just a new name.
It's a name that has been used for a long while in Numerical Analysis. After all, saying Taylor expansion doesn't help much when integrating DE's (in some sense even Runge-Kutta methods are a kind of Taylor expansion), for instance, whereas AD does give a lot more information.
