The way I understood it, Nintendo never lost such case in Japan, so when they sue, they are very certain in victory.
I'm not a fan of usual Nintendo bullshit when it comes to YT over-zealousness over their IPs, but in this case, another dev pretty much gave them the middle finger and hoped they would get away with it.
It would be terrible if they get them over some game mechanic patent (why those things can be patented at all is beyond ludicrous), but hey - karma is a bitch.