So do you have "complete" credits or are you just going to dismiss MobyGames' credits because reasons?That mobygames link does not have the complete credits. Sony Santa Monica didn't only just give Giant Sparrow office space to make their game. You can have a look at its complete credits and you can see very key technical members within that played a huge role like Tim Moss being their chief of technology along with creative leads from SSM providing help. The same is true how Sony San Diego do things. You gave an example of a network engineer... that's also considered a developer. Creative advice is another example you gave which is influencing game design. These all count towards development of a title and hence "co-developed" is a perfectly apt way to describe the relationship between Bartel Jones and Sony San Diego.
Looking at those The Unfinished Swan credits, I see the (now former) head of SSM's external development group (Nathan Gary), a number of producers and consultants and then SSM/WWS management. I'm not really seeing these key technical members you're talking about. Tim Moss was in the management section, as one of the two Chiefs of Technology at Sony Santa Monica, there's no reason to believe he had a significant role on The Unfinished Swan. As an aside, SSM's external dev group are now Annapurna Interactive, so do you think they co-develop all the games they publish (like Edith Finch) or was it somehow different when they were part of SSM?
And finally, no, just because they may have received some help in the form of a network engineer or some creative advice, doesn't mean they co-developed the game. Come on. If that were the case then I guess you think The Last of Us was co-developed by a dozen different companies because of all the outsourcing Naughty Dog does, right? That's completely ridiculous.