Normally reverse mode automatic differentiation is used and is called backpropagation since everything old has to have a new and shiny name in machine learning a/k/a continuous optimization ;)
I think this is a very bad thing, but basically what happens when things become "commoditized".
I feel it's the same with web developers who have no formal background in Computer Science. All these frameworks reinventing "paradigms" that have been studied since the 60's.