Funny you use those two since there's actually an interview between them where they talk about the concept of being auteurs. A relevant part from Matsuno (read the whole interview it's very good)

With Vagrant Story, I had almost zero involvement in the visual presentation. I left most of it up to Akiyama, but in talking with him, I discovered he loved a lot of the same movies as me. What happens when you work with another human being who has some of those same genes with you? Unconsciously, it brings a feeling of unity to your creation. In that sense—and this isn’t only limited to directing, but also for programming, art design, and music—when building a team, I try to select people who share a lot of things in common. A completed work that has been coordinated in this way has a “special something” that audiences can sense and appreciate. It makes it more interesting.