I see what David Gerard is saying, it's just that having a map is very different from having to find the optimal solution to TSP on that map. We look at maps all the time and don't solve TSP on them.
there is a lot of missinformation going around in the crypto-currency world. i think that after this privacy claim was debunked it morphed into the idea, that lightning was mathematically impossible. somewhere along the line TSP was added to the explanation. 0wing says TCP is "unsolvable NP-hard" which doesnt make much sense. well, its hard to understand the path of rumors. lightning might yield a constant factor scaling improvement with worse security and worse convenience, but it can work.