If you lie constantly, people shouldn't believe you. Absolutely not. But it's the wrong moral for this story. The right moral, in my opinion, would be a lot longer. It would go, If you care about your sheep and tell somebody to watch them, and he proves two times in a row that he's not ready for the job, then you should fire him or keep checking whenever he hollers.
Outrage at the fable and a silly idea started me writing. I thought, Wouldn't it be funny if a wolf and shepherd's pie were in a story together? Betsy is about as different from the Boy as can be. She would never cry wolf unless there was a wolf. Alas, she's pitted against the cleverest wolf on Rosenrise Mountain!