x86_64 is a proprietary, licensed ISA. Both Intel and AMD’s microarchitectures implementing it are proprietary. Apple didn’t design their own ISA; they’re using ARM (which is also proprietary).
Consoles may be using x86_64, but they are not PCs. Very similar to PCs, but then so are Apple’s ARM machines. Both Apple’s computers and PCs use standard components and interfaces like USB, PCIe, and UEFI.
But all of this is beside the point. Even if Apple did build everything from scratch, why should that give them the right to lock down their computers? My point here isn’t about what is technically legal under current legislation, but what should be legal based on our values as a society.