I don't know about F keys, but usually the alternative (apple) layout exists because there are differences in the character keys layout between Apple and MS layouts, and someone using Apple hardware might not get the results they expect when using Windows. What exactly these are for English I don't know.
Tom, thanks for the hint! It looks like Apple keyboard layout is not shipped with Windows 8, but is installed as part of BootCamp 5.0.5033 (\Drivers\Apple\AppleKeyboardInstaller64.exe).
Device Manager reveals the Hardware ID of the Apple Keyboard: USB\VID_05AC&PID_0236&REV_0090&MI_00.
\AppleKeyboardInstaller64\KeyMagic64.inf has a line for the device: HKR,"KeyboardTable","VID_05AC&PID_0236",0x00000001,%INTERNAL%,%ANSI%,%NEW_LAYOU T%,%DELAY_RESET_WELLSPRING%,1; M97 and M98.
AppleKeyboardInstaller64.exe archive though contains no explanation why additional keyboard layout is added to the system. Maybe Apple anticipates that some unusual layout might be installed, and adds a regular one that matches the letters on MacBook keyboard, just in case.
Maybe Apple anticipates that some unusual layout might be installed, and adds a regular one that matches the letters on MacBook keyboard, just in case.
I think they are anticipating that when you choose the MS US English layout in Windows, there may be some keys on the Apple keyboard that do not generate the character printed on them or otherwise expected. If that turns out to be the case and it is a problem, then you can try switching to the (apple) layout.