you cant give yourself dark oak fence with commands

you need to type give @s dark oak fence and there is only dark oak fence gate

Working as intended. Dark oak fences have their own data value branching off from the regular fence. If you want a dark oak fence specifically, you need to run the command '/give @s fence [amount] 5'. This is the same for all wood types as well, not just dark oak. They occupy data values 0-5.