No, you don't know what you are talking about, as usual. Do some math. If you add the increased dimensions to accommodate a 5.1" diagonal screen, keeping the same depths of each model, you wind up with approximately 11% more volume for a battery inside. If the battery originally took up only 10% of the original space, then you can easily fit a battery that is twice as big inside a phone that has a screen that is only 0.4" larger on diagonal dimension. THAT is engineering.
Whatever...Cheap and disposable are the words of the day at Apple. Take Bendgate for example.