I disagree with this because who came up with the idea and who wrote the story are often two separate things. That's why comics often separate the two in the credits page. For example, an issue of Spider-man would have a "created by stan lee and steve ditko" credit but "written by nick spencer and art by Ryan ottley" or whoever did the issue.
So Nomura should get the created "by" credit for XV because his ideas for Versus 13 laid the framework for XV. But another director and other writers came in and shaped his ideas their own way. They also did the actual work of writing the game script page to page (etc) and how the game turned out "roses and thorns" are theirs more than his.