I keep running into folks who say, “You need to start with a sentence — preferably 25 words or less — that sums up your book.” Unless I’m going to write, “Boy meets girl, stuff happens, they live happily ever after,” I don’t think that’s going to work for me.
The idea is brilliant; you boil your story down to its essential elements and communicate that to the listener, who will hopefully be intrigued enough to ask for a full/buy the book. It is absolutely something a writer needs to do as they send their precious work out into the cold, cruel world. My argument isn’t with that. My argument is about when the writer needs to do that.