on iphone you can't even install software that apple doesn't explicitly allow.
they would love to extend this to all computing devices to remove control
That's not really true. Apple is encroaching freedom of software choice on their devices, but they know that they can't extend the same kind of security policies to the desktop. You can disable secure boot on Macs and even run Linux if you like. Additionally, it's a bit difficult but if you disable SIP you do get access to the entire systems file system. They're a shitty company when it comes to repair-ability and their walled garden, but they know they can't extend this to the desktop, or else they would disqualify themselves from the developer market (where they are quite popular).