I guess everyone is missing the part that we haven't actually confirmed the composition of the atmosphere and whether it corresponds to one of their simulated atmospheres to such a degree that their results are applicable *or* that the simulated atmosphere is actually usable by life of any kind.
For all we know, it has an atmosphere made entirely of nitrogen or one that doesn't have sufficient carbon dioxide to sustain a greenhouse effect and has substantially frozen out.
This is purely hype of a simulation based on mostly made up stuff to determine what compositions *could* work to sustain a temperature-habitable environment. Mars is nearly temperature-habitable but no one would ever claim that it is 'habitable'. The only really interesting bit is the ability to, in the future, spectroscopically analyze the atmosphere and plug the values into their simulation to get results based in reality.