It's not moving the goalposts, it's describing the scale of the problem. If fusion won't be addressing a significant fraction of the CO2 problem, it will be because it's inferior to the non-fossil energy sources that are. In which case, why is it even needed?

Nuclear fission looks unable to compete with renewables at current prices in almost all the world. There's a zone around Poland where it does the best. But even those zones go away as renewables and storage proceed down their experience curves. If there are very minor niche uses, fission would work just fine vs. fusion, particularly in high latitude countries that are already members of the nuclear club.