"If your membership is terminated, you may no longer submit apps to the App Store, and your apps still available for distribution will be removed. You will also lose access to the following programs, technologies, and capabilities:"
[...]
"- Engineering efforts to improve hardware and software performance of Unreal Engine on Mac and iOS hardware; optimize Unreal Engine on the Mac for creative workflows, virtual sets and their CI/Build Systems; and adoption and support of ARKit features and future VR features into Unreal Engine by their XR team"
That is a statement that Apple made saying they will stop all help they give to Epic getting UE running on all Apple hardware. With the other stuff in the letter it makes it very clear that the problem is not just one for Epic Games, but all of Epic.
You can read it yourself - https://cdn2.unrealengine.com/epic-v-apple-8-17-20-768927327... (Apple's letter starts on page 51 of the PDF)