I don't know. I've long had the same question. It's considered a "turnover on downs."
Now we can unleash all the halftime adjustment Red made!
Regarding your sig, I've actually read somewhere recently that statistically speaking, it makes much more sense to go for it on 4th down every time instead of punting. But no coach is willing to take the heat for such a thing. I think there's a High School coach using the strategy and it's working well apparently.