The fundamental motivation for the app id concept is that part of the value that InboxSDK provides is cushioning the developer from version conflicts, both from Gmail updates and from multiple extensions that all use InboxSDK. So we use app ids + a custom error reporting mechanism to aggregate anonymized error reports in order to figure out incompatibilities + reach out to the developer as appropriate.
You're welcome to make the app id opaque. Also feel free to file an issue for making a setting to disable the app id - definitely not opposed to adding it as an option given interest.
This is impressive! For folks who are worried about what this says about App Engine's security - historically the JVM level sandboxing was one part of an overall sandboxing story (not surprisingly, very similar to Chrome's setup) and my understanding, although haven't been on the team for a decade at this point, is that the JVM-level restrictions have been effectively replaced by a gVisor-based solution.