What's exactly wrong with that tho? Also, remember when the Skull Knight tried to kill Griffith and instead tore a hole between worlds? It'll be interesting to see how far their 'white-luck' extends, won't it.
There isn't really anything wrong with it, only the fact that it begs different questions in the case.
Time is a complicated subject in either case. I do find it more interesting, personally, to think of the characters as having choices, even if those choices have, essentially, been preordained. In this sense, it isn't that Griffith
had to do what he did, it's that he
would. So, he did make a choice, in a sense, because he could have acted otherwise, but chose not to. That he chose not to was foreseen, but to me, it's more interesting if this was not determinate, blindly so, but rather is just knowledge of the way things are likely to turn out.
I mean, we'll see how it works, because Guts should be dead, but he isn't. So, we don't know if we are in a totally determinate world or not. It's still more interesting to me if the characters are actually making choices, even if they fail at making ones they haven't been driven to. It's basically a question of "locus of control."