Not sure it's the same thing. Under FAA Flag operations (international flights) flights are required to have the fuel to destination plus 10 percent plus 30 minutes plus fuel to an alternate if required. And an alternate is always required if the leg is more than 6 hours no matter the weather under flag rules (we won't get into the island rule.) Imagine a flight ANC to HKG and say it's 9 hours. You would need 9 hours fuel plus 30 minutes plus 54 minutes plus an alternate. And say it's 6 hours to Tokyo. Your initial release to Tokyo says you need 6 hours fuel plus 30 minutes plus 36 minutes and throw in an alternate. But you are planning to go to HKG so you'd have ~10 hours fuel onboard. About an hour out of Tokyo dispatch sends new paperwork to continue to HKG. Now you only need 4 hours plus 30 minutes plus 24 minutes. And if fuel was tight and the weather good dispatch could drop the requirement for an alternate. In the end you save carrying about an hour's fuel. It's done all the time by US airlines in international ops.