Not according to TFA. Do you have a source for your counterassertion? I doubt Tyler Rogoway would get such a point of fact incorrect - even when I've disagreed with his analysis I've never found him to be dishonest.
I have prior training as both aero and nuclear engineer and there are obvious design space solutions? NERVA was an open cycle reactor meaning the propulsive intake air made direct contact with the core, and ablation is what caused radioactive exhaust. Closed cycle designs are more typical in production systems in which a high temperature conventional radiator would transfer heat from the core to the jet reaction chamber. The article is flat out wrong/misinformed.