Skullgirls just licensed GGPO and used 2D sprites. As I understand it rollback netcode is taxing on the game which means devs have to make sacrifices in other areas, typically graphics, in order for rollback netcode to work efficiently. Since most modern fighters are fully 3D the game itself is pushing the system to its limits already because, unlike most GGPO releases, it's not an old arcade game ported to a current gen system. You don't just slap it on the game and go.
So I'm guessing the Kagemusha code was designed to try and create a balance between the game looking good and having rollback netcode. Plus, I'm not sure if GGPO even works well with UE4 or 3D games in general. I think there's only one 3D game, Rising Thunder, that uses GGPO and that game looked very barebones graphically.
I knew he acknowledged it but I wasn't aware he said the devs knew. That's good.