To me it feels like he probably had more to do with the different motivations between the characters and the nature of what the Elden Ring was and how that was related to the key figures of the story, without spoiling anything. And I guess the fact that some characters are kind of incest babies or bastards as I recall.

I do think he was mostly intended as a name drop, and that if you just told someone to make some of the dynamics of the different warring families something like he would write they could pull it off, but if you get deeper into the lore on that it was feel someone like Martin had a hand. Would still be among the greatest games of all time if you’re into Souls games if he hadn’t though.

Until someone says something it’s kind of hard to say what he really did. He himself did say he didn’t do much, just some general direction on key themes and presumably the Game of Thronesy parts like the warring of the different shard barer siblings and such.