Okay I didn’t have access to paywalled article before.

The NYT article is about one specific study that’s a review of archival material. It doesn’t actually seem to suggest that it was a “publicity stunt” or “theater” as OP suggested. Rather, it says that NASA believed that the threat was very real. The threat was real enough to hold a “high level conference” (held by National Academy of Sciences). The outcome there was also that “the risk was real and the consequences could be profound”.

So, the major spending on the quarantine system wasn’t out of nowhere.

The study conclusion seems to be more that it would be nearly impossible to contain the threat if it existed. But, that wouldn’t mean that the precautions taken were only for show — just that it would be really fucking hard to stop. And with the hypothetical microbe, they couldn’t know anything about means of transmission or lifespan — so the precautions could have some value.

Even in the failure of their quarantine procedure, it still demonstrated that they thought it was (in principle) important:

“24 workers were exposed to the lunar material that the facility’s infrastructure was supposed to protect them from; they had to be quarantined”

It wasn’t security theater so much as it was just quarantine procedure that had many gaps, failures, and trade offs.