Doesn't sound interesting at all, as the two matters are unrelated.

Apple isn't charging for use of the iOS platform SDKs; the developer agreement is much more vague and weasely about what they're charging for, being the developer's "agent and/or commisionaire".

Per-sale licensing for a copyrighted (or patented) work is pretty normal and done in many industries. Apple's agreement doesn't specify any fees for licensing at all.

Moreover, if they would actually admit what they were nominally charging for then someone could create a third party implementation of whatever that is, people would want to be able to use that instead of paying the fee, and what is their excuse supposed to be then?

The case has been about whether preventing others from competing on pricing is anticompetitive not whether having pricing should be illegal in itself. Whether that's about the App Store or the SDK it would be extremely odd to suddenly expect Epic to instead try to argue it's the payment model that's the problem not the anti-competitiveness of only allowing 1 option.