I have done 3 guitars with the hot rod truss rods that are adjustable at the heal but I have seen some places where they rout the slot right to the end of the heal. I usually just rout it until the adjustment nut and than drill a hole for it. Would it be better just to rout through? I would think the truss rod would fall out though... I am in a position now where I either have to patch up the end of the neck and drill a hole or patch it up and rout to the end or I may just start another neck.
I'd keep with drill the hole, looks much neater. Anyway if you did route all the way through the rod wouldn't fall out if installed correctly.