EFI is not exclusive to Macs. It was developed by Intel and has been deprecated in favor of UEFI.
Most UEFI images will have legacy support for BIOS services.
There is basically no difference between a modern Mac and a PC - except for Mac OS X, which can be run on "Hackintoshes".
Not if your (U)EFI firmware is capable of booting BIOS-booted operating systems as well as (U)EFI operating systems (like IBM System x Server Firmware).
So they appear to be moving over to "not being IBM PC compatible". Which is perfectly valid.
I never said that PCs are called PCs because they ARE IBM PC compatible, only said they are called PCs because in the past "IBM PC compatible" defined their category.
There is basically no difference between a modern Mac and a PC - except for Mac OS X, which can be run on "Hackintoshes".