The NR-R-NR wire looks like this, you can see the little bumps where they weld normal wire to the coil Kanthal.
The Diver has a ceramic cup that sits half way up where the slots are, the coil wires run down the sides to the base in the bottom unit. You don't want the wires in the base heating up or adding a lot of extra resistance so they use NR-R-NR to coil it with.
The Ithaka is the same way the NR wires run down the side of the ceramic cup to the 510 connector which you can see in the center of the picture.
FT has premade coils if you want to get into that type of device.
Good to hear about the no leaking, I am going to have to get one of those!