Go back and read the First day of Q&A, I think we answered most of that then and yesterday. Of course you are correct, an airborne protein that reacts with the test doesnt necessarily mean it represents a functioning virus. Out of an abundance of caution is a phrase we have heard repeatedly in recent years. I think the safe, efficient, and effective way forward would be everybody wears a bandana when in public.
I just thought it was interesting as it talks about what they thought an effective dose was for SARS-cov1.