The NR conducts with no resistance as normal. The R wire then glows as normal (not with juice of course). As soon as it touches the metal channel it grounds and effectively becomes an NR wire from that point down the metal channel.
One negative is you HAVE to make sure to tuck the R wire under the wick to make sure the contact to the metal channel stays. If you accidentally go above the wick and it lifts, it'll continue to stay R until contact is made. But this is easy as even a double leg we practice laying under wick. But a positive remains. For example, you try a different setup (say twisted). You wrap too many coils and leave yourself with a 1.7ohm coil. You lift the wick in metal channel, uncoil once or twice to your liking, trim excess, and lay back down. I've done that and in 30 seconds corrected the resistance to what I liked.
One negative is you HAVE to make sure to tuck the R wire under the wick to make sure the contact to the metal channel stays. If you accidentally go above the wick and it lifts, it'll continue to stay R until contact is made. But this is easy as even a double leg we practice laying under wick. But a positive remains. For example, you try a different setup (say twisted). You wrap too many coils and leave yourself with a 1.7ohm coil. You lift the wick in metal channel, uncoil once or twice to your liking, trim excess, and lay back down. I've done that and in 30 seconds corrected the resistance to what I liked.