I’m not entirely in disagreement with this technicality, and it doesn’t put the matter to rest – there are still longer term and more permanent ways this can be resolved, not just a court ruling about executive discretion.
The more important case is against the EPA – whether they could assume the authority to force power plants to switch to different power generation methods. And the answer is no – the EPA was trying to usurp authority it was never granted and that Congress rejected giving it when writing the Clean Air Act. And Kagan’s dissent is that Congress isn’t smart enough to regulate climate.