To be fair he probably thought that he would simply adopt ranked ballots which does not have the fringe party problem. He did not expect the push back on the need for a referendum which made ensuring ranked ballots would be the choice much tougher.
If you set a minimum vote threshold with PR it does not have a fringe party issue, that's just bs, but you can bet that if ranked ballots had that issue and were also still very good for liberals he would have welcomed it anyway.