I don't even understand what that link is on about. I did none of that - I just downloaded the game onto my iPad having already purchased it on iPhone, then logged into my Nintendo account when it prompted me to at startup. The full game and my progress were instantly on my iPad.
I followed the advice on that link but on my second device I can't link to my Nintendo account, I only have the option to create one. So I'm not going to risk paying another £8 on the purchase screen. I shall delete it and wait until something more concrete happens.
it worked for me, but i agree, wait as you should't have to pay twice. The fact that it is so tricky is a joke.