You guys always see these things through your console exclusivity glasses that forget that these platform holders are still just publishers and that these are very standard practices within the publishing business (i.e. picking up a game that was already in development for you to publish).
Moneyhatted third-party exclusives (something that can only be the case in the context of a platform holder) are just deals made between the partners relations groups of each company involved, while deals like Bayonetta 2 and Stellar Blade (situations that are very common in the video game publishing industry) involve these publishers (Nintendo and SIE) directly funding and managing the project, while also handling all related sales and marketing operations.