Call me silly, but. After extensively rewatching the trailer, I think I've noticed some differences in the Clash System. Around the 1:45 mark, there are a couple of clashes between Slashes and Heavy Slashes. The character using the Slash attack gets into short semi stun state as if blown back. And then with both attacks of the same category clash, they get evened out.
..I'm probably reading too much into this, tho.