When you buy a phone, you definitely own all the atoms in it. You can take it apart and use the bits to make jewelry. You can take all the phones you have and assemble them into a piece of wall art. Apple has no say in what you do with the object.
But your belief that physical ownership of the object should mean you can make it do anything you want is… bounded by your actual capability to do so.
You can probably extract some of the parts of your phone and reuse them - maybe with care and patience you could figure out how to use the screen, or the battery, or the camera as part of another device. Again, not something Apple can stop you doing.
But expecting to be able to use a device to do something you want to merely because you know the potential to do so is inside is an unrealistic expectation. A cotton t-shirt might contain enough thread to be able to be woven into a pair of shorts, but you can’t complain to the manufacturer that the way they made the t-shirt makes it hard for you to turn it into shorts. They sold it to you in a useful, valuable configuration. They’re not obligated to make it easy for you to reconfigure it to your will.