What advantage? I'm always a bit shocked to see people say this without qualifying it at all.
On the contrary, Apple has to do a lot of greenfield work by refusing standards like UEFI, Vulkan and normal filesystems. They end up reinventing the wheel just to support the same featureset that Qualcomm, Nvidia, AMD and Intel all generally planned for.
Is it more work to support a completely proprietary boot path or three different "standard" boot paths?
Advantage of commitment and integration. Apple doesn't need to worry about critical vendors not cooperating because sticking with x86 is less risky.
Apple’s advantage is being the last vertical computer company from the 1980s speaks for itself. having control of the hardware and the operating system software with the ability to create new ecosystems is their advantage in comparison to hardware or software only companies, Note: the tech world would be a better place if Sun, SGI, Digital, Acorn, Motorola of Schaumburg, Illinois had been able to survive the Microsoft/Intel onslaught.