Except that games like Pong teach you the basic mechanics of making anything. If you start deep into coding a massive game, you will be making mistakes that you would have made with Pong. This means every mistake you made will have to be fixed later, taking up more time since the code will all be dependent on what you base it off of. If you want to start making a game, you should start simple or at least make your code modular so that if you need to fix any major mistakes, it will take less time to fix the rest of the game.
In my experience, of course. I dove right into it and always had to rewrite what I wrote before, which took more time than if I started simple.