These two statements contradict each other. In a managed project there is no project.pbxproj or build.gradle.
Perhaps you ran npx expo prebuild or npx expo run:android/npx expo run:ios at some point? If so, that would have generated the native projects, effectively switching you to the bare workflow. At this point, most changes in app.config.js would not have any effect.
Have a look at this old post of mine which might help: