Doesn't matter if the game was made prior to the merger, because even then, they would have taken it down if Fair Use did not apply to it. Maybe Fair Use could lend a factor, but I don't know how it applies with entire challenges.
But seeing as they did not take it down, it's a good thing. You are in the clear so stop fretting , k?
I got a thing from Starz for Guyver , but its far better than them taking it down and getting a copyright infringement strike. Mine will go in a few months, and that's from that douche bag who dressed like Ronald McDonald and scared some kids at a McD's. What a bitch.
If it doesn't tell you to take it down then you're good. In terms of Tekken, NamcoBandai's very lenient when it comes to that stuff. I mean, the game wouldn't be as big as it is if it weren't for all the combo vids, right?