Well basically, When you get bootcamp and then buy windows if basically gives you 2 operating systems on your mac that you switch between.
E.g You want to play BF4 you switch to Windows. You want to do something that isn't on Windows you switch to OSX Mountain Lion
It wouldn't have said that because the only operating system BF4 runs on is Windows
You could have simple looked at the hardware requirements for the BF4 PC game
here http://bf4central.com/battlefield-4-system-requirements/
Battlefield 4 system requirements
The minimum PC system requirements for Battlefield 4 are expected to be:
Dual core CPU (Intel Core i5 or AMD “Bulldozer”).
At least 4 GB main system memory
Graphics card with at least 512 MB of VRAM and support for DirectX 10
30+ GB of harddrive space
Windows Vista
Recommended system requirements
The recommended PC system requirements for optimal visual quality and frame rates:
Quad core CPU (Intel Core i5 or i7) at 3 Ghz
4 GB memory (8 GB for 64-bit operating systems)
A modern DX11 graphics card with 2+ GB of video memory, GeForce 600 series or Radeon 7000 series
Windows 7 64-bit operating system (Windows 8 is supported as well)
30+ GB of free harddrive space
