Topic on Talk:Hotline Miami 2: Wrong Number
GeneralFailer, the link you gave stating that Dennaton would "talk to Abstraction" refers to the question how the in-game level editor would work. Since the game is based on Abstraction's GameBaker and SilverWare, Wedin is about to ask Abstraction if they could develop something like the thing the questioner asked for.
Silent, the reason Abstraction's splash is first is because HM2 uses Abstraction's GameBaker and SilverWare (as stated above) and thus put it right in front. This is the same case as when you make a game in the free version of Unity, just because it is there doesn't mean that the Unity3D team worked on the game.
Abstraction is _not_ considered a developer of the game. The reason they are for the first game is that they ported the game from PC to PS3,4,Vita and afterwards patched the PC version.