My Macbook Pro 13 inch with retina early 2015 model is configured for both filevault 2 and Windows 10 enterprise with bitlocker enabled.
I did a lot of reading and found a couple of guides, one was the one you listed. I think from memory it missed a step needed in El Cap about new security to allow the partition to be created.
I had to boot into osx recovery and run csrutil disable to allow the partition software to run correctly