They're assisting by making sure the resources the team needs are available to them. If that means providing them a sound studio, creative advice, a network engineer, outsourced art or whatever then that's what they do. Hell, if it means providing them an office space to work in, like SSM did with Giant Sparrow and thatgamecompany, then that's also what they do. By producer I didn't mean an actual producer, I meant that their role is to provide the resources the dev team needs so they can get their shit done.
As far as Drawn to Death goes, look at its credits and tell me how many SSD (not SSM) programmers and artists you see there:
http://www.mobygames.com/game/playstation-4/drawn-to-death/credits
I'm not being disingenuous or depreciating the role Sony San Diego's external dev team played, I think they do a fantastic and necessary job, but what you're doing is actually downplaying the actual dev teams by insisting that they were co-developed with major studios when in reality that's far from the case.