Answering 1): I did not set this flag to NO for any target in XCode. When I attempted to do so for NotificationService I could not compile this target. Only after setting it in Podfile inside post_install call I was able to compile Notification Service with expo dependencies.
Answering 2): My local Pods-NotificationService.debug.xcconfig doesn't contain this flag.

Sorry, my mistake. I should remove this unnecessary space shortly.

I don't think either of my questions has been answered in detail.

My first question: does this flag get set to NO for some other target? To answer this, you will have to go through every single related target (the pods for the NotificationService across debug/release, and the actual NotificationService itself) and figure out what the flag is set to, and then share that information here.

My second question: you need to determine IF IT MATTERS that we are setting this to NO. What does it mean to set this to YES vs. NO? How does it work if one target with YES includes one with NO, or the other way around?

Your answer will probably need to be multiple paragraphs long, with links to documentation.

There are two changes here compared to master branch:

1. post_install hook is moved from target 'Comm' scope to global Podfile scope
2. some lines are added that disable APPLICATION_EXTENSION_API_ONLY flag to enable CommonCpp sources compilation in 'NotificationService' target.

Let me explain why those changes should not raise concern.
Ad. 1) According to this doc: https://www.rubydoc.info/github/CocoaPods/Core/Pod%2FPodfile%2FDSL:post_install post_install is a hook applied just before XCode project is written to disk. According to this doc: https://www.rubydoc.info/gems/cocoapods-core/0.34.1/Pod/Podfile/DSL Podfile hooks always exist in global scope. Even if this post_install hook was written inside target 'Comm' scope its behaviour would be the same as if it was in global scope. This is even more confirmed by the fact that an attempt to write multiple post_install hooks (e.g. each per target) leads to errors: https://github.com/CocoaPods/CocoaPods/issues/6172.
Ad. 2) Now that we established that we cannot have multiple post_install hooks and the one that we have should be in global scope we can admit it is impossible to use this flag anywhere else.

Build settings in the XCode project refer to targets: Comm and NotificationService. This line changes build settings for pods. I did not modify this line and according to the explanation above it has alway been that we exclude both architectures for all pods. I do not know why it is that, but it is not related to any change introduced in this diff. Target 'Comm' excluded only amr64 architecture before I started to work on this issue and the very recent changes I introduced were to unify excluded architectures for both Comm and NotificationService. Would you like me to try whether we can exclude i386 arch for XCode targets as well?