You misread the article. There are open redirectors on .gov domains (like a naive hit-counter), the shortener just goes .gov -> .gov. Now the shortener blacklists the open redirects as short link targets.
It's a legitimate question. Bitly should do a GET request to the resource before creating the 1.use.gov link. This is standard practice. It should work quite well in this case because the open redirectors under .gov are just poorly programmed; they're not actively trying to avoid detection.
