Yes, that's what the judge warned in the ruling. Epic got what they asked for on this point because they were technically correct on the merits, but both the judge and the appeals court were skeptical that demanding it would do anyone any good:
> IAP is the method by which Apple collects its licensing fee from developers for the use of Apple’s intellectual property. Even in the absence of IAP, Apple could still charge a commission on developers. It would simply be more difficult for Apple to collect that commission.
> In such a hypothetical world, developers could potentially avoid the commission while benefitting from Apple's innovation and intellectual property free of charge. The Court presumes that in such circumstances that Apple may rely on imposing and utilizing a contractual right to audit developers annual accounting to ensure compliance with its commissions, among other methods. Of course, any alternatives to IAP (including the foregoing) would seemingly impose both increased monetary and time costs to both Apple and the developers.
That metric doesn't work accurately even in the simplest case (buying an app), let alone for more nuanced transactions -- in-app purchases, subscription tiers, etc.
It's unclear how how Apple-the-middle-man can insert itself to effectively rent seek from customers/developers now.
Charging both sides of a market _typically_ results in crash of the two sided (platform-hosted) market. With iOS and Android being basically near feature parity, this is to Google's favor.
So they know total app installs as well as the installs purchased from the App Store.