I went through the process described in my initial post and decided to make it faster and more scalable: manually going through hundreds of requests in Charles was very cool for research and educational purposes, but it also took me a lot of time to find "interesting" requests coming from a single app. If you only want to record traffic coming from a specific app, close all apps, "Clear flows" and then open the desired app. However, I don't want to make false claims saying that this app was responsible for Apple's request – that endpoint is not accessible directly for any app except for iOS itself, so in order to get the information from it an app needs to call a dedicated Apple API method and have corresponding permissions.