Please report such discrepancies in the documentation to support, so it can get fixed.
To address the issue you described: The only thing I can imagine is that you overlayed or customized some things based on AEM 6.0, which have changed with AEM 6.4, so that the overlays are not working properly anymore.
Have you run through the inline upgrade or did you start with a fresh AEM 6.4 instance and deployed your content and application on top of it via packages/grabit/...?