Yeah exactly, isn't it causing way more E waste when people have to replace their phones every 3-5 years because of a battery only? Hopefully now in the future you can replace that battery and use your phone even longer. Resulting in only batteries being replaced which could probably be recycled somehow (I'm no expert on this, so no clue if what I'm saying is correct :P )

It depends on the amount of extra batteries that are made. In 2022, 225 million iPhones were sold. If an extra battery for every phone was produced, but only half of those consumers ever buy a new battery then we are looking at over 100 million wasted batteries. Then eventually all of those 225 million consumers would get a new phone anyways, so it still becomes waste at some point. I'm sure they will get better at predicting how many extra batteries to make eventually though. I do wonder how much it's needed these days though. I get a new device every ~ 18 months but my spouse uses devices for ~ 5 years before getting a new one. She usually gets a new one just because of newer features, battery degradation doesn't seem to be as much of an issue anymore.