In regards of NASA taking it seriously, my null hypothesis would be that reporters misunderstand NASA just as much as everything else about fungi.

If I understand the linked NASA press releases correctly, they are talking about using a mix of regolith, cyanobacteria and fungi as part of the outer shell of a habitat. The mycelian network of the fungi binds the loose regolith together, forming a strong and somewhat flexible material, with the fungus working a bit like the cement in a concrete mix. And because fungi don't form from nothing you add cyanobacteria that create "fungus food" (presumably some sugar) from water and CO2 (I'm sure you need to add a bit more than that, but that might be beyond the scope of a press release)

This really has nothing to do with radiation-absorbing fungi at all, except for one remark how the melanin in radiation-eating fungi could provide further shielding.