The newsfeed doesn't need to be the core business for NYTimes to sell full-page advertisements, nor does it need to be the core business to sell stories on preferred topics.

Sure. They could sell a lot of things that aren't core to their business. But why would they? Their next marginal dollar doesn't come from squeezing the news organization; in fact, the way things are trending, news is basically looking like it'll be a loss leader for them.