> “A practical lunar or Martian habitat must integrate pressure retention, gas tightness, mechanical support, thermal regulation, radiation shielding, dust protection, repairability, and resource recycling,” the paper notes. “These requirements will likely require hybrid architectures” that include both the yeast foam and more traditional structures.

So no. They could very well need 99% "traditional" structures. All they did was find a way to make a semi-biological expanding foam. And that's cool. But it seems to be using Mars as a marketing crutch

Is radiation a non-factor here given the simplicity of the organism?

1 atm = 14 psi which is not structuraly difficult to achive, but it needs to be very robust and absolutly impermiable to gasses. And there are many possible fabric solutions that can be shipped to mars as ready to inflate habitats with air locks.Systems would need to be installed, and very likely the only good and safe places will be smaller craters with steep tall sides. Step.2 would be tenting small craters, and then perhaps growing structures could become practical. But if the upgraded starship can land 100 tons on mars, then that would deliver habitats big enough for crews, crops, and manufacturing. The key will be finding a spot with, year round solar, metals, and water in a very small radius, without that it's just a stunt.