Earlier quoted context omitted.
All products even with ownership come with rules and regulations. Houses can’t be arbitrarily changed. Cars have governors. Scissors shouldn’t be run with. Ownership of an iPhone is not different. It just has special rules attached. If you don’t mind breaking the warranty, please jailbreak your iPhone and install whatever apps you’d prefer.
The US courts have consistently held that it is perfectly legal to do anything to your privated owned things that are not public. Your house example is wrong, because that has public viewing concerns on a plot of land. And your car example is incorrect. I could make any changes at all to a car, that is not put on public roads. That has nothing to do with the manufacturer putting restrictions on your car.
If you want to cherry pick arguments we can do this all day. The reality is Apple is just doing what every manufacturer has done for millennia!