Thanks Cowboy. Never dawned on me to be that specific but yea - What cowboy said.
Yep, his post is
extremely significant because there are people like me who have utilities that create bootable media, but if the image they create is not UEFI-compliant, then the Surface won't boot it.
For example, I used PE Builder to build and create a customized WinPE bootable environment. When I burned the image to a USB flash drive, it would boot no issues on my old ThinkPad W700 laptop; however, the Surface Pro would not see it at all. I kept on investigating and chasing down this problem until I eventually learned that the problem was due to the fact that the WinPE image that was created was not UEFI-compliant.
I wish this wasn't the case and that the Surface Pro would boot non-UEFI USB drives, but it is what it is and my workaround has been to purchase and use an additional USB drive (non-boot; just data) in order to get the customized boot environment that I require.