Do you have a source for this? Reading the decision here it seems like both the developers and the consumers have standing to sue, although for slightly different reasons [0].

[0] from the decision: "Here, some downstream iPhone consumers have sued Apple on a monopoly theory. And it could be that some upstream app developers will also sue Apple on a monopsony theory. In this instance, the two suits would rely on fundamentally different theories of harm and would not assert dueling claims to a “common fund,” as that term was used in Illinois Brick. The consumers seek damages based on the difference between the price they paid and the competitive price. The app developers would seek lost profits that they could have earned in a competitive retail market. Illinois Brick does not bar either category of suit."