This seems to be incorrect.

Apple is not moving to tighten control; the restriction has been there for a while. I believe Apple banned non-Apple in-app purchases when they launched their in-app purchase system (if not before then).

Edit: The article does say Apple "has told some applications developers … that they can no longer … let customers have access to purchases they have made outside the App Store."

However, that doesn't seem to be sourced, and when the point is reiterated in the fourth paragraph, only the existing restriction is mentioned: "Apple told Sony that from now on, all in-app purchases would have to go through Apple, said Steve Haber, president of Sony’s digital reading division."