Usage of WebViews for web logins in mobile apps are not recommended due to security and usability reasons documented in RFC8252. Google has done the same for Google Sign-in in 2021.
Frame busting is for mobile app RPs/clients who are still using web views and not moved to in-app browsers yet. As the OIDC provider for RPs, NDI core will also start supporting in-app browsers and will soon discontinue the support for the web views.
