Platinum Games owns the Astral Chain IP. Nintendo just publishes it. So it is not a co-owned IP. The copyright goes to both of them because Nintendo is the publisher. It is not the same as Nintendo owning the IP.
If Nintendo's name is in the copyright notice alongside Platinum's, then Nintendo owns half the IP. Meaning they have a say on what they can do with it. Astral Chain is owned by both Platinum and Nintendo.
Actually I don't see how it is any different to any other publisher. If a game is developed by X, you have to credit X, even if it is published by Y and Y owns the IP.
So SEGA and Platinum for Bayonetta for instance. I actually think in this case Platinum even co-owns the IP.
I doubt Bandai Namco can release a Souls game without From Software. There seems to be a co-ownership in place too.
When Bungie split with MS they made a deal about Halo-ownership, which indicates beforehand Bungie had some rights on the IP. Later on they published Destiny through Activision, but had a time-limited deal with Activision after which they regained full control over the IP.
I actually cannot think of an example of an IP developed not in-house by a publisher and the publisher takes full control of said IP. It might happen, but it seems Nintendos stance on this isn't so extraordinary in the industry.