The inspection says that findChildrenByClass only calls its super method. This is true, but it also enables package-level access to that method, which will fail when the method is removed (see Test2). This results in annoying errors when accepting the "Delete Unnecessary Method" fix...

class Test extends PsiElementBase {

  @Override
  @NotNull
  protected <T> T[] findChildrenByClass(Class<T> aClass) {
    return super.findChildrenByClass(aClass);
  }
}

class Test2 {
  void test(Test t) {
    final Object[] children = t.findChildrenByClass(PsiElement.class);
  }
}

Issue was resolved