As of Angular 16, they are well reported (in error) by the Angular compiler.
In addition, the Angular language service allows auto-import of components/directives/pipes.
See: https://blog.angular.dev/angular-v16-is-here-4d7a28ec680d#56a5
As of Angular 19, they are well reported (in warning) by the Angular compiler.
Additionally, the Angular language service allows auto-remove them.
See: https://blog.angular.dev/meet-angular-v19-7b29dfd05b84#816c