Hawker, I suspect Knox wasn't ready in time, but the rest of the software and hardware was. I'm speculating of course, but I can t think of any other logical reason. It does seem odd that the bootloader was open on early firmwares up until comparatively recently.
Samsung Galaxy S4 GT-I9505
ROM STOCK UK -I9505XXUEMJ7 UPDATED FROM STOCK 4.3 VODAFONE WITH ODIN KNOX STILL 0x0
Samsung Galaxy Note 3 SM-N9005
FOR NOW: STOCK FIRMWARE