Additional protection would keep them 99% dry instead of 90% dry even in a storm. Right up to the point where they have to deliver a letter, where they would be 0% dry.
It's more important to be able to get in and out easily.
"Protection" does not mean absolutely proof against. But even more, "calling BS" implies that the statement is not just wrong, but deceptive, and I completely disagree with that premise. (Which is additionally a claim it would be idiotic for them to make for an occupant likely wearing a rain coat.)
It's more important to be able to get in and out easily.