

Stock price is really just a present value of future expected earnings. Buying Coke for $100 is because you think the earnings of that share in the future is worth $100. So yes, if the company makes an announcement that it isn’t as profitable, the price will go down, because buyers won’t want to pay the same for an asset that is returns less than it was expedited to.
Yes, there are complications. Shorts, futures, non dividend yielding shares, and more make it more muddied. At the end of it though, the future expected earnings are what is being bought and sold.
Because, for a touch screen, the screen itself IS the user interface. Imagine while holding with one hand, you want to reach your thumb to the opposite corner to hit a button. Even if the body of the phone is the same, a larger screen will need a bigger reach for your thumb. That is primary issue.