I do agree that the FF name is more popular in the West nowadays and they attached some big names to it so it may do better here. That said, I'm one of those who will say that it did decently with those box office numbers for a release meant to be straight-to-Bluray, no matter how many times duckroll says it did terrible. I imagine most people saying those numbers were good are people comparing it to Western box office numbers they are more familiar with.
If you were to take the opening weekend numbers for Disney CGI movies for the same amount of screens, Kingsglaive did about ~40% of that. Considering those movies reach the widest audience possible, I'd say 40% is pretty good. Not to mention tripling its ticket sales after 10 days is good in any box office. This is all said in comparison to Western box office numbers at a glance, which is why I'm asking for perspective with someone familiar with Japan's box office. I also may be biased in my arguments because I'm tired of the whole doom and gloom/"bomba" culture here on GAF(and the rest of the internet).