As a senior game developer, i can tell you that no game released nowadays is EVER complete. And trying to making a game complete is like trying to write all the digits of Pi. It cant be done, you just have to draw the line somewhere and say "this is good enough". We work until our employers pry our hands from the keyboards and force us work on a new project. Then we sneak back and work a little bit more on the old one either because we are ashamed of the quality or because we love the project. And we HAVE to move on to new projects, otherwise game development would not be economically feasible and there would be no AAA projects such as the ones mentioned in TFA.
And the point of doing minor DLC is not to make money from it directly. The point is to give a promise to the consumers that there will be DLC shortly, and make them hold on to their copies instead of reselling them, which would bring zero money to the publisher. This is not some theory of my own, it is what our publishers tell us when they are ordering us to do minor DLC. Why they charge so much for stuff that would have done it's job perfectly when released for free is beyond my understanding though.
It's funny that the example in TFA where the true strategy was most obvious, the DLC for Alan Wake, was where the author was most happy with the product...