The only time it's not silly is when said dependencies are not just non-free, but covered under an NDA. If the API is under NDA then they can't release the code that uses the APIs. AIUI this is why FOSS games don't get ported to console, even though there might be people willing to fork up the money to pay for devkits and SDKs.

My guess is that it's the dependencies for the game engine. They use a custom engine but with how fast they got it up and running I'm guessing it's based on a pre-existing game engine which would almost certainly get it put under NDA.

What secret sauce APIs are there to protect on the consoles? I guess the DRM side they might want to keep as secret as possible, but everything else strikes me as boring standard stuff. Here is how you draw a triangle, register an achievement, pop up the console store, whatever.