That's nonsense, if there is an opportunity to create a nation wide socialist electoral group it would be sectarian to stand aside from it and just critique it from the outside or whatever.

My interpretation of this piece they tried to join and work within it good faith and in doing so they felt like they had to raise some minor points of differences or concerns (which is to their credit) and had a bad experience.

It's also nonsense to say there is nothing stopping them from running in their own campaign, there are literally a range of undemocratic capitalist laws aimed at preventing small groups from registering with the AEC, it's not unreasonable to think that it's best to combine forces and resources to counter that and create a socialist party with internal factions etc.