I just finished the game... I found all treasure and crucifix, but didn't get all the soul, what does it do? as there are No achievement for finding all the souls...
And how does the achievement for Nightmare difficulty Trigger? how do you know which mission you finished on Nightmare?
And what is the point of getting new victory point, my skill are all maxed out...
And I guess for the last character attribute to be maxed, I will just need to finish 8 mission and at the end of each mission I'll get a new Victory point for the attribute?
It is kind of confusing... lol
It's probably just for the extra challenge. I stopped playing after I beat hard mode but the way you put it I would just assume that.
Bottom line is that you are thinking too hard about a simple thing instead of being grateful. In giving enough VP in easy/normal/hard to max all techniques, the developers made it so that even the most casual player can play through any difficulty and have plenty of points to spend, even if they don't bother collecting a single thing. There need not be an achievement for something like soul collecting to be included in the game.
What if you had to complete every mission on normal and have all collectibles (and souls) just to have barely enough VP to max only 1 technique and 2 skills? Bet you would find that annoying and even more confusing.
In my opinion anyway.