I imagine the post you're replying to means that they don't want a presentation to look too planned and staged (which feels insincere). Of course you want to practice, but you want to make it look natural and effortless at the same time.

Like a stand-up comedian who makes it sound like he's telling an anecdote (that just happened to come to mind) for the first time, even though he's told it a million times on stage before.

("Acting is acting like you're not acting.")