Seems this has returned, check generated methods below.

I filed this as a REGRESSION.
It is the same bug as #225088 but since that has been fixed and verified...
It also looks as it occurs only with certain object types (alas, not Object but with Collection (see below))

@Override
  public boolean remove(Object o) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
  }

  @Override
  public boolean containsAll(
                             Collection<?> c) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
  }

  @Override
  public boolean addAll(
                        Collection<? extends SetType> c) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
  }

  @Override
  public boolean retainAll(
                           Collection<?> c) {
    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
  }