I don't know how to nail the BootCamp version but the drivers were downloaded to my USB flashdrive as part of the Bootcamp setup process. I think the most important updated drivers for mid June MBA are those for Broadcom BC43xx wifi, Intel HD5000 GPU and trackpad. I've seen some comments about the trackpad (though looks identical) being totally different from previous MBA's.I'm not sure it's only drivers. Perhaps Apple also did changes to their EFI firmware to be more compatible. Would be interesting to find out. What BootCamp version did you download?
I dug deeper into the standard SATA AHCI controller driver installed in device manager, in fact this is simply for the 3rd party controller resides on the PCIE SSD instead of the onboard Intel controller. In this sense, it is not a direct indication of EFI mode.