In my opinion, it's terrific advice, and not just for speakers. Being authentic is what your customers respond to. If you pretend to be something you're not, your mask will slip at some point.
You don't need to copy phrases or funny lines from elsewhere.
You don't need to cut and paste content from other people's blogs and websites.
You don't need to make false claims about being "The world's leading...." or "The UK's most sought after......".
You don't need to pretend that you just had an idea when you really heard it years ago somewhere else.
You need to write your own stuff.
You need to have your own point of view.
You need to be authentic and honest.
You need to be a first-class you.