What? Why does this have any meaning at all?

There's a reason why you aren't allowed any alcohol before flying - it's because your judgement is impaired long before any other signs of non-sobriety appear.

(Also, disasters sober one up considerably.)

"The captain wasn't slurring his words or staggering around, so it's OK he deliberately avoided a drug and alcohol test," is not even a little convincing.

I do note you follow this up later, but there really isn't any upshot. Seemingly this same thing could happen today.

In particular, the follow question is raised: "If you were a pilot or copilot who had just been in a fatal accident, what possible reason would you have for deliberartely ducking blood tests for two days unless you knew they would come out dirty?"