From what I understand from the article (I just read it quickly, still waiting on my reading list), shrinkResources trueit is only necessary to reduce the size of the APK by removing unused resources , but this is not a formal requirement for Instant Apps. I think the toolchain cannot decide whether the resource will not be used in the library, since the final APK has not been created.
So, if there are no unused resources in your project, this should not be a problem and can be deleted.
-, ( Instant Apps , Google IO): , , - APK, . , shrinkResources true APK, . , APK, shrinkResources true .