- 2012 and older models only support legacy BIOS Mode. There is varying degree of 'EFI'ness in these, but they are not UEFI-compliant.
- Late 2013-2014 models support both EFI and BIOS, and default is BIOS. These are the first models which are UEFI.
- 2015 and later models only support EFI and UEFI-compliant.
BC Assistant knows all this. It is highly recommended that you use BC Assistant only, to install Windows on Macs. Using Alt/Option to interrupt the default installation process is not recommended, unless you know what you want.
Jan 30, 2015 OSX Tutorial - How to enable 'Create a Windows 7 install disk' option in Boot Camp Assistant. Make a Boot Camp USB on an Unsupported Mac.YOSEMITE. Duration.
On a 2012 MBP, you need to use BIOS mode, because CSM-BIOS exports the Cirrus devices correctly but EFI does not.